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Background: Lateral discoid meniscus accounts for most meniscal tears in children 10 years of age and younger. The role of bony morphology in discoid meniscus has been previously studied in a limited capacity using radiographs., Purpose: To use magnetic resonance imaging to measure features of the femoral condyles and tibial plateaus in patients with discoid meniscus to assess potential determinants of symptoms and subsequent surgery and to compare with matched controls to investigate age-related changes in bony features., Study Design: Cross-sectional study; Level of evidence, 3., Methods: After institutional review board approval, detailed morphology of the femoral condyles and tibial plateau was measured in 177 patients (3-18 years of age; 56% female) with confirmed lateral discoid meniscus. Measurements from 269 participants (3-18 years of age; 55% female) with asymptomatic knees were used as controls. Two-way analysis of variance with Holm-Šídák post hoc was used to compare measurements between discoid menisci and matched controls. Independent t tests were used to compare aspects of bony morphology within the discoid meniscus cohort., Results: Compared with controls, patients with a lateral discoid meniscus had a larger bicondylar width and notch width (7- to 10-year-old and 15- to 18-year-old age groups; P < .05), larger tibial plateau width (11- to 14-year-old and 15- to 18-year-old age groups; P < .001), and smaller lateral ( P < .02) and coronal ( P < .02) tibial slopes across all age groups. Among patients with a discoid meniscus, larger bicondylar width, larger tibial plateau width, larger notch width, and a flatter lateral femoral condyle were associated with pain ( P < .005) and lateral meniscal tears ( P < .02). Larger notch width and notch width index were also associated with subsequent surgery ( P < .05)., Conclusion: There are clinically significant abnormalities in bony morphology in patients with a discoid meniscus, including larger femoral condyles and tibial plateaus and a flatter tibial plateau. Additionally, femoral size, femoral curvature, and tibial plateau size may influence the likelihood of knee pain, meniscal tear, and need for surgery. These findings highlight the importance of bony morphology in discoid meniscus pathophysiology in children and adolescents. Such measurements may also aid radiographic detection of discoid meniscus and guide decisions regarding the timing of potential surgical intervention., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: D.E.K. is a paid consultant for Miach Orthopaedics and DePuy Synthes and receives education support from Kairos Surgical. B.E.H. has received education payments from Arthrex, Kairos Surgical, and Pylant and is a consultant and stock owner for Imagen Technologies. M.S.K. has received consulting fees and royalties from OrthoPediatrics and Ossur; royalties from El Secier and Wolters Kluwer; speaking fees from Smith & Nephew; and support for education from Kairos Surgical Inc. A.M.K. is a paid consultant of Miach Orthopaedics. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Background: Although meniscal injury is common after anterior cruciate ligament (ACL) injury, the underlying process in different meniscal regions remains unclear., Purpose: To investigate macroscopic and histological alterations in different meniscal regions in an ACL transection (ACLT) rabbit model., Study Design: Controlled laboratory study., Methods: ACLT was performed on New Zealand White rabbits. Both the medial meniscus (MM) and the lateral meniscus (LM) of the ACLT knees were obtained at 8 (n = 6) and 26 (n = 6) weeks postoperatively. MM and LM collected from nonoperated knees were considered 0 weeks (n = 6) postoperatively. Menisci were then divided into posterior, central, and anterior regions for macroscopic (width) and histological (hematoxylin and eosin, safranin O/fast green, collagen type 2 [COL2]) analysis., Results: The macroscopic widths of MM and LM increased and then decreased over 26 weeks postoperatively, with all 3 MM widths at 8 weeks significantly wider than at 0 weeks (posterior: P < .01; central: P < .05; anterior: P < .05). In the MM, chondrocyte-like cell density increased and then decreased postoperatively, whereas in the LM, it decreased and then remained almost unchanged. Cell density was significantly higher in the central MM region at 8 weeks than at 0 weeks ( P < .05). Glycosaminoglycan (GAG) and COL2 percentages of MM and LM decreased from 0 to 8 weeks and then returned to nearly normal levels at 26 weeks postoperatively. In the MM, the GAG percentage in the posterior ( P < .05) and central ( P < .01) regions and the COL2 percentage in the posterior region ( P < .05) was significantly lower at 8 weeks than at 0 weeks., Conclusion: After ACLT in rabbit meniscus, the extracellular matrix (ECM) initially decreased and then increased to almost normal. Additionally, there were significant differences in the ECM percentage in the posterior and central regions of the MM in comparison with other meniscal regions between 0 and 8 weeks postoperatively., Clinical Relevance: The results indicate that the time for meniscal injury after ACL injury is important, and attention should be paid to the posterior and central regions of the MM after ACLT.

Background: Bone bruises observed on magnetic resonance imaging (MRI) can provide insight into the mechanisms of noncontact anterior cruciate ligament (ACL) injury. However, it remains unclear whether the position of the knee near the time of injury differs between patients evaluated with different patterns of bone bruising, particularly with regard to valgus angles., Hypothesis: The position of the knee near the time of injury is similar between patients evaluated with 2 commonly occurring patterns of bone bruising., Study Design: Descriptive laboratory study., Methods: Clinical T2- and T1-weighted MRI scans obtained within 6 weeks of noncontact ACL rupture were reviewed. Patients had either 3 (n = 20) or 4 (n = 30) bone bruises. Patients in the 4-bone bruise group had bruising of the medial and lateral compartments of the femur and tibia, whereas patients in the 3-bone bruise group did not have a bruise on the medial femoral condyle. The outer contours of the bones and associated bruises were segmented from the MRI scans and used to create 3-dimensional surface models. For each patient, the position of the knee near the time of injury was predicted by moving the tibial model relative to the femoral model to maximize the overlap of the tibiofemoral bone bruises. Logistic regressions (adjusted for sex, age, and presence of medial collateral ligament injury) were used to assess relationships between predicted injury position (quantified in terms of knee flexion angle, valgus angle, internal rotation angle, and anterior tibial translation) and bone bruise group., Results: The predicted injury position for patients in both groups involved a flexion angle <20°, anterior translation >20 mm, valgus angle <10°, and internal rotation angle <10°. The injury position for the 3-bone bruise group involved less flexion (odds ratio [OR], 0.914; 95% CI, 0.846-0.987; P = .02) and internal rotation (OR, 0.832; 95% CI, 0.739-0.937; P = .002) as compared with patients with 4 bone bruises., Conclusion: The predicted position of injury for patients displaying both 3 and 4 bone bruises involved substantial anterior tibial translation (>20 mm), with the knee in a straight position in both the sagittal (<20°) and the coronal (<10°) planes., Clinical Relevance: Landing on a straight knee with subsequent anterior tibial translation is a potential mechanism of noncontact ACL injury.

Background: Meniscal tears in the avascular region are thought to rarely heal and are a considerable challenge to treat. Although the therapeutic effects of a pulsed electromagnetic field (PEMF) have been extensively studied in a variety of orthopaedic disorders, the effect of a PEMF on meniscal healing has not been reported., Hypothesis: PEMF treatment would promote meniscal healing and prevent osteoarthritis progression., Study Design: Controlled laboratory study., Methods: A total of 72 twelve-week-old male Sprague-Dawley rats with full-thickness longitudinal medial meniscal tears in the avascular region were divided into 3 groups: control (G con ), treatment with a classic signal PEMF (G classic ), and treatment with a high-slew rate signal PEMF (G HSR ). Macroscopic observation and histological analysis of the meniscus and articular cartilage were performed to evaluate the meniscal healing and progression of osteoarthritis. The synovium was harvested for histological and immunofluorescent analysis to evaluate the intra-articular inflammation. Meniscal healing, articular cartilage degeneration, and synovitis were quantitatively evaluated according to their scoring systems., Results: Dramatic degenerative changes of the meniscus and articular cartilage were noticed during gross observation and histological evaluation in G con at 8 weeks. However, the menisci in the 2 treatment groups were restored to normal morphology, with a smooth surface and shiny white color. Particularly, the HSR signal remarkably enhanced the fibrochondrogenesis and accelerated the remodeling process of the regenerated tissue. The meniscal healing scores of the PEMF treatment groups were significantly higher than those in G con at 8 weeks. Specifically, the HSR signal showed a significantly higher meniscal repair score than did the classic signal at week 8 ( P < .01). Additionally, the HSR signal significantly downregulated the secretion levels of interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in the meniscus and synovium as compared with the control group. When compared with the 2 treatment groups, G con had significantly higher degeneration scores (G con vs G classic , P < .0001; G con vs G HSR , P < .0001). The HSR signal also exhibited significantly lower synovitis scores compared with the other two groups (G con vs G classic , P < .0001; G classic vs G HSR , P = .0002)., Conclusion: A PEMF promoted the healing of meniscal tears in the avascular region and restored the injured meniscus to its structural integrity in a rat model. As compared with the classic signal, the HSR signal showed increased capability to promote fibrocartilaginous tissue formation and modulate the inflammatory environment, therefore protecting the knee joint from posttraumatic osteoarthritis development., Clinical Relevance: Adjuvant PEMF therapy may offer a new approach for the treatment of meniscal tears attributed to the enhanced meniscal repair and ameliorated osteoarthritis progression.

Background: A description of the precise locations of ligamentous and myotendinous injury patterns of acute posterolateral corner (PLC) injuries and their associated osseous and neurovascular injuries is lacking in the literature., Purpose: To characterize the ligamentous and myotendinous injury patterns and zones of injury that occur in acute PLC injuries and determine associated rates of peroneal nerve palsies and vascular injuries, as well as fracture and dislocation., Study Design: Case series; Level of evidence, 4., Methods: We retrospectively identified all patients treated for an acute multiligament knee injury (MLKI) at our level 1 trauma center from 2001 to 2018. From this cohort, all patients with PLC injuries were identified. Demographics, involved ligaments and tendons, neurovascular injury, and presence of fracture and dislocation were compared with the larger multiligament knee cohort. Incidence and location of injury of PLC structures-from proximal to midsubstance and distal injury-were recorded., Results: A total of 100 knees in 100 patients were identified as having MLKIs. A total of 74 patients (74%) had lateral-sided ligament injuries. Of these, 23 (31%) had a peroneal nerve palsy associated with their injury; 10 (14%), a vascular injury; and 23 (31%), a fracture. Patients with PLC injuries had higher rates of peroneal nerve injury as compared with those having acute MLKIs without a PLC injury (31% vs 4%; P = .005). Patients with a complete peroneal nerve palsy (n = 17) were less likely to regain function than those with a partial peroneal nerve palsy (n = 6; 12% vs 100%; P < .0001). Complete injury to the lateral collateral ligament (LCL) occurred in 71 of 74 (96%) PLC injuries, with 3 distinct patterns of injury demonstrated. Fibular avulsion of the LCL was the most common zone of injury (65%), followed by femoral avulsion (20%) and midsubstance tear (15%). Location of injury to the LCL was associated with the rate of peroneal nerve injury, with midsubstance tears and fibular avulsions associated with higher rates of peroneal nerve injury., Conclusion: MLKIs with involvement of the PLC are more likely to suffer peroneal nerve injury. The LCL is nearly always involved, and its location of injury is predictive of peroneal nerve injury. Patients with a complete peroneal nerve palsy at presentation are much less likely to regain function.

Background: Bone bruising of the posterolateral tibial plateau and the lateral femoral condyle sulcus terminalis has a well-established association with anterior cruciate ligament (ACL) tears. Impaction fractures of the femur and tibia may occur in these locations; however, there is a paucity of literature describing these fractures., Purpose: The primary objective was to quantify the incidence, size, and location of impaction fractures of the posterolateral tibial plateau and lateral femoral condyle in patients with primary ACL tears. The secondary objective was to investigate the association between impaction fractures and concomitant meniscal and ligamentous injuries., Study Design: Case series; Level of evidence 4., Methods: Patients with available magnetic resonance imaging (MRI) scans who were treated for primary ACL tear by a single surgeon were identified. MRI scans were reviewed with denotation of posterolateral tibial and femoral condylar contusions and displaced impaction fractures. Measurements of the lateral tibial plateau were taken in all patients with displaced lateral tibial plateau fractures and in a subset of control patients without tibial plateau fracture present to characterize the size and location of the bony lesion. Associations of impaction fractures with concomitant meniscal or ligamentous injuries were evaluated through use of chi-square testing., Results: There were 825 knees identified with available MRI scans. Lateral tibial plateau bone bruising was present in 634 knees (76.8%), and lateral femoral condyle bone bruising was present in 407 knees (49.3%). Posterolateral tibial plateau impaction fractures were present in 407 knees (49.3%), and lateral femoral condylar impaction fractures were present in 214 knees (25.9%). Patients with posterolateral tibial plateau impaction fractures were older than patients without these fractures (42.6 vs 32.7 years; P < .001), whereas patients with lateral femoral condylar impaction fractures were younger (23.8 vs 32.7 years; P < .001). There were 71 knees (8.6%) with a posterolateral tibial plateau impaction fracture with greater than 10% loss of lateral tibial plateau depth, and this group had an increased incidence of lateral meniscus posterior root tears (22.1% vs 12.0%; P = .02)., Conclusion: Posterolateral tibial plateau impaction fractures occurred with a high incidence (49.3%) in patients with primary ACL tears and demonstrated an increased association with lateral meniscus posterior horn root tears as their size increased. Lateral femoral condylar impaction fractures occurred in 25.9% of patients with primary ACL tears and entailed an increased incidence of lateral meniscal tears and medial meniscal ramp lesions.

Background: Although the femoral tunnel position is crucial to anatomic single-bundle anterior cruciate ligament (ACL) reconstruction, the recommendations for the ideal femoral footprint position are mostly based on cadaveric studies with small sample sizes, elderly patients with unknown ACL status, and 2-dimensional techniques. Furthermore, a potential difference in the femoral ACL footprint position and ACL orientation between ACL-ruptured and ACL-intact knees has not been reported in the literature., Hypothesis: The femoral ACL footprint position and ACL orientation vary significantly between ACL-ruptured and matched control ACL-intact knees., Study Design: Cross-sectional study; Level of evidence, 3., Methods: Magnetic resonance images of the knees of 90 patients with an ACL rupture and 90 matched control participants who had a noncontact knee injury without an ACL rupture were used to create 3-dimensional models of the femur and tibia. The ACL footprints were outlined on each model, and their positions (normalized to the lateral condyle width) as well as ACL orientations were measured with an anatomic coordinate system., Results: The femoral ACL footprint in patients with an ACL rupture was located at 36.6% posterior and 11.2% distal to the flexion-extension axis (FEA). The ACL orientation was 46.9° in the sagittal plane, 70.3° in the coronal plane, and 20.8° in the transverse plane. The ACL-ruptured group demonstrated a femoral ACL footprint position that was 11.0% more posterior and 7.7% more proximal than that of the control group (all P < .01). The same patients also exhibited 5.7° lower sagittal elevation, 3.1° higher coronal plane elevation, and 7.9° lower transverse plane deviation (all P < .01). The optimal cutoff value of the femoral ACL footprint position to prevent an ACL rupture was at 30% posterior and 12% distal to the FEA., Conclusion: The ACL femoral footprint position might be a predisposing factor to an ACL rupture. Patients with a >30% posterior and <12% distal position of the femoral ACL footprint from the FEA might have a 51.2-times increased risk of an ACL rupture.

Background: Osteochondral allograft transplantation (OCA) is a successful knee joint preservation technique; however, the effects of defect size and defect size:condyle ratio (DSCR) are poorly understood., Purpose: To quantify clinical outcomes of isolated OCA of the knee based on defect size and DSCR., Study Design: Cohort study; Level of evidence, 3., Methods: Data from patients who underwent OCA of the knee without major concomitant procedures by a single surgeon were analyzed at a minimum follow-up of 2 years. Osteochondral defect size was measured intraoperatively, and femoral condyle size was measured with preoperative imaging. Patient-reported outcomes, reoperations, and survival rates were analyzed per defect size and DSCR, comparing males and females and patients <40 and ≥40 years old., Results: Sixty-eight patients were included, of whom 57% were male (mean ± SD: age, 34.5 ± 10.3 years; follow-up, 5.2 ± 2.6 years). Mean osteochondral defect size and DSCR were 3.48 ± 1.72 cm 2 and 0.2 ± 0.1, respectively. Defect size was larger among males as compared with females (3.97 ± 1.71 cm 2 vs 2.81 ± 1.16 cm 2 , P = .005), while DSCRs were not significantly different between sexes ( P = .609). The cohort as a whole demonstrated improvements in the following scores: Lysholm, International Knee Documentation Committee, Knee injury and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and 12-Item Short Form Health Survey Physical ( P < .05). There were 27 reoperations (39.7%) at a mean of 2.5 ± 1.92 years and 8 failures (11.8%) at a mean of 2.62 ± 1.3 years. Mean DCSR was higher among patients with graft failure (0.26 ± 0.20 vs 0.19 ± 0.07, P = .049). After stratification by age, failures among patients ≥40 years old were associated with a larger defect size (mean 5.37 ± 3.50 cm 2 vs 3.22 ± 1.32 cm 2 , P = .03) and higher DSCR (mean 0.30 ± 0.25 vs 0.19 ± 0.06, P = .05) when compared with nonfailures. Failures among patients <40 years old were not significantly associated with defect size or DSCR ( P > .05) as compared with nonfailures., Conclusion: Patients undergoing isolated OCA transplantation demonstrated significant clinical improvements and a graft survival of 88.2% at 5.2 years. Failures overall were associated with a larger DSCR, and failures among patients ≥40 years old with a larger DSCR and larger defect size. Increasing defect size among males was positively correlated with some improved outcomes, although this was not maintained in analysis of the DSCR, suggesting similar prognosis after OCA regardless of sex., Clinical Relevance: Failed osteochondral allografts are associated with larger defect sizes and defect:condyle ratios in this study, providing additional information to surgeons for appropriate patient consultation.

Background: Meniscal ramp lesions have been defined as a tear of the peripheral attachment of the posterior horn of the medial meniscus (PHMM) at the meniscocapsular junction or an injury to the meniscotibial attachment. Precise anatomic descriptions of these structures are limited in the current literature., Purpose: To quantitatively and qualitatively describe the PHMM and posteromedial capsule anatomy pertaining to the location of a meniscal ramp lesion with reference to surgically relevant landmarks., Study Design: Descriptive laboratory study., Methods: Fourteen male nonpaired fresh-frozen cadavers were used. The locations of the posteromedial meniscocapsular and meniscotibial attachments were identified. Measurements to surgically relevant landmarks were performed with a coordinate measuring system. To further analyze the posteromedial meniscocapsular and meniscotibial attachments, hematoxylin and eosin and alcian blue staining were conducted on a separate sample of 10 nonpaired specimens., Results: The posterior meniscocapsular attachment had a mean ± SD length of 20.2 ± 6.0 mm and attached posteroinferiorly to the PHMM at a mean depth of 36.4% of the total posterior meniscal height. The posterior meniscotibial ligament attached on the PHMM 16.5 mm posterior and 7.7 mm medial to the center of the posterior medial meniscal root attachment. The meniscotibial ligament tibial attachment was 5.9 ± 1.3 mm inferior to the articular cartilage margin of the posterior medial tibial plateau. The posterior meniscocapsular attachment converged with the meniscotibial ligament at the most posterior point of the meniscocapsular junction in all specimens. Histological staining of the meniscocapsular and meniscotibial ligament PHMM attachments showed similar structure, cell density, and fiber directionality, with no qualitative difference in the makeup of their collagen matrices across all specimens., Conclusion: The anatomy of the area where a medial meniscal ramp tear occurs revealed that the 2 posterior meniscal attachments merged at a common attachment on the PHMM. Histological analysis validated a shared attachment point of the meniscocapsular and meniscotibial attachments of the PHMM., Clinical Relevance: The findings of this study provide the anatomic foundation for an improved understanding of the meniscocapsular and meniscotibial attachments of the PHMM, which may help provide a more precise definition of a meniscal ramp lesion.

Background: Limited information in basic science and clinical trials exists to determine if ligament healing may be accelerated with the use of biological adjuvants, such as platelet-rich plasma (PRP). However, there has been widespread acceptance of PRP for use in clinical practice, despite an inadequate understanding of its biological mechanism of action., Purpose: To determine whether a single dose of PRP could accelerate ligament healing and correspondingly improve histological characteristics and biomechanical properties when injected immediately postoperatively into the injured medial collateral ligament (MCL) of New Zealand White rabbits., Study Design: Controlled laboratory study., Methods: Eighty skeletally mature New Zealand White rabbits (160 knees) were used. The MCL was torn midbody to simulate a grade 3 tear. After an acute injury of the MCL, the administration of autologous PRP at 3 different platelet concentrations (0 million/uL, platelet-poor plasma [PPP]; 0.6 million/uL, 2 times the baseline [2× PRP]; and 1.2 million/uL, 4 times the baseline [4× PRP]) was performed and compared with a saline injection control in the contralateral knee. Histological analysis and a biomechanical endpoint characterization were utilized to assess ligamentous healing and compare it to a sham surgery group., Results: The PPP ( P = .001) and 4× PRP ( P = .002) groups had a significantly lower collagen subscore than the sham surgery group. No other differences were observed among the treatment groups, including the vascularity subscore and overall ligament tissue maturity index score. Compared with saline-injected contralateral knees, the maximum load for PPP and 2× PRP was not significantly different ( P = .788 and .325, respectively). The maximum load and stiffness for knees treated with 4× PRP were significantly less than for the saline-treated contralateral knees ( P = .006 and .001, respectively)., Conclusion: One single dose of PPP or 2× PRP at the time of injury did not improve ligament healing. In addition, 4× PRP negatively affected ligament strength and histological characteristics at 6 weeks after the injury., Clinical Relevance: The current practice of treating knee ligament injuries with PRP may not improve healing at low doses of PRP. The decreased mechanical properties and histological appearance of the torn MCL suggest that high doses of PRP decrease the quality of repair tissue. Further in vivo studies are necessary to determine the dosing and timing of PRP administration after a ligament injury before the widespread use of PRP to treat ligament injuries is recommended.

Background: Meniscal extrusion is related to degeneration of the native knee joint. However, the clinical effect of the phenomenon after meniscal allograft transplantation (MAT) has not been clearly identified. Purpose/Hypothesis: The purpose of this study was to evaluate the change in meniscal extrusion in both the coronal and sagittal planes after lateral MAT through the midterm follow-up period. We hypothesized that meniscal extrusion does not progress during the midterm follow-up period., Study Design: Case series; Level of evidence, 4., Methods: A total of 46 patients with a mean follow-up of 51.1 ± 7.1 months were included in the study. The patients underwent lateral MAT using the keyhole technique. Postoperative magnetic resonance imaging (MRI) was performed at 6-week, 1-year, and midterm (3- to 5-year) follow-up. In the coronal plane, the absolute value of meniscal subluxation and the relative percentage of extrusion (RPE) were measured. In the sagittal plane, meniscal subluxation was measured as the absolute and relative anterior cartilage meniscal distance (ACMD) and posterior cartilage meniscal distance (PCMD). The joint-space width (JSW) on weightbearing radiographs with 2 different knee positions was measured preoperatively and at 1-year and midterm follow-up. The Lysholm score was assessed at the same time points., Results: In the coronal plane, the mean absolute meniscal extrusion at 6-week, 1-year, and final follow-up was 2.90 ± 0.94, 2.85 ± 0.97, and 2.83 ± 0.89 mm, respectively, and the mean RPE was 27.0% ± 9.4%, 27.1% ± 10.1%, and 27.8% ± 9.7%, respectively. There were no statistically significant differences in absolute and relative coronal extrusion among the 3 time periods ( P > .05). The percentage of patients with meniscal extrusion (≥3 mm) was 37.0% at 6-week follow-up and 34.8% at 1-year and final follow-up. In the sagittal plane, the mean absolute ACMD was 2.59 ± 1.75, 2.58 ± 1.85, and 2.37 ± 1.60 mm, respectively, and the mean relative ACMD was 20.7% ± 13.1%, 20.6% ± 13.8%, and 19.0% ± 12.2%, respectively, at the 3 follow-up time points. The mean absolute PCMD was -1.23 ± 3.34, -1.28 ± 3.08, and -1.42 ± 2.77 mm, respectively, and the mean relative PCMD was -10.3% ± 25.9%, -11.0% ± 24.6%, and -12.2% ± 23.2%, respectively, at the same time points. Sagittal extrusion was not significantly different between the time points ( P > .05). The mean JSW at 2 days preoperatively, 1 year postoperatively, and midterm follow-up was 5.40 ± 1.07, 5.44 ± 1.04, and 5.43 ± 0.98 mm, respectively, on anterior-posterior radiographs with full extension, and it was 4.90 ± 0.94, 4.94 ± 0.98, and 4.89 ± 0.96 mm, respectively, on posterior-anterior radiographs with 45° of flexion. The mean JSW values were not significantly different between the 3 different time points ( P > .05). The mean preoperative Lysholm score was 58. 9 ± 8.3; the score increased to 90.4 ± 9.7 at 1 year postoperatively and 90.5 ± 10.1 at final follow-up, which is a significant improvement compared with the preoperative status ( P < .05). There was no statistically significant difference between the scores at the 2 postoperative time points ( P > .05)., Conclusion: This study demonstrated that extrusion of the meniscal allograft did not significantly progress either in the coronal or sagittal plane after lateral MAT during the midterm follow-up period.

Background: Subchondral bone overgrowth has been described with variable frequency after microfracture, but little systematic information is available about the clinical incidence, risk factors, or clinical relevance of this phenomenon., Hypothesis: Subchondral overgrowth (1) occurs with high incidence and various degrees after microfracture, (2) is associated with risk factors, and (3) affects clinical outcome score and failure rate., Study Design: Cohort study; Level of evidence, 3., Methods: A total of 84 patients undergoing microfracture in the knee were prospectively followed up to 6 years postoperatively through use of cartilage-sensitive magnetic resonance imaging to detect the incidence of subchondral bone overgrowth. The quantity of the overgrowth was graded systematically and was then correlated to patient and lesion characteristics, surgical technique, validated functional outcome scores, and failure rate., Results: Subchondral bone overgrowth was observed in 62% of patients at a mean of 22 months after surgery. Most bone overgrowth (64%) was low grade and developed during the first 12 months after microfracture. Risk factors for bone overgrowth included high body mass index, defects on the lateral femoral condyle, and aggressive debridement of the calcified cartilage layer. Knee injury and Osteoarthritis Outcome Score results were not significantly different between patients with or without subchondral bone overgrowth. However, 93% of patients who failed microfracture demonstrated osseous overgrowth, and patients with osseous overgrowth showed a significantly higher failure rate (25%) than patients without overgrowth (3.1%; P < .01)., Conclusion: Subchondral bone overgrowth is frequently observed after microfracture surgery but is mostly of low grade. Several risk factors were identified that can affect the incidence of this phenomenon. Importantly, subchondral overgrowth is associated with an increased rate of postoperative failure after microfracture., (© 2016 The Author(s).)

Background: The treatment of concomitant cartilage lesions in anterior cruciate ligament (ACL)-injured knees is debatable., Purpose: To evaluate the effect of debridement or microfracture (MF) compared with no treatment of concomitant full-thickness (International Cartilage Repair Society [ICRS] grades 3-4) cartilage lesions on patient-reported outcomes after ACL reconstruction., Study Design: Cohort study; Level of evidence, 2., Methods: Six hundred forty-four patients who underwent primary unilateral ACL reconstruction and had a concomitant full-thickness cartilage lesion treated simultaneously by debridement (n = 129) or MF (n = 164), or underwent no treatment (n = 351) of the cartilage lesion, registered in the Norwegian and Swedish National Knee Ligament Registries from 2005 to 2008 were included. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used to measure patient-reported outcomes. At a mean follow-up of 2.1 ± 0.2 years after surgery, 357 (55%) patients completed the KOOS. Linear regression analyses were used to evaluate the effect of debridement or MF on the KOOS., Results: No significant effects of debridement were detected in the unadjusted or adjusted regression analyses on any of the KOOS subscales at 2-year follow-up. The MF treatment of the cartilage lesions had significant negative effects at 2-year follow-up on the KOOS Sport and Recreation (Sport/Rec) (regression coefficient [β] = -8.9; 95% confidence interval [CI], -15.1 to -1.5) and Knee-Related Quality of Life (QoL) (β = -8.1; 95% CI, -14.1 to -2.1) subscales in the unadjusted analyses. When adjusting for confounders, MF had significant negative effects on the same KOOS subscales of Sport/Rec (β = -8.6; 95% CI, -16.4 to -0.7) and QoL (β = -7.2; 95% CI, -13.6 to -0.8). For the remaining KOOS subscales of Pain, Symptoms, and Activities of Daily Living, there were no significant unadjusted or adjusted effects of MF., Conclusion: MF of concomitant full-thickness cartilage lesions showed adverse effects on patient-reported outcomes at 2-year follow-up after ACL reconstruction. Debridement of concomitant full-thickness cartilage lesions showed neither positive nor negative effects on patient-reported outcomes at 2-year follow-up after ACL reconstruction., (© 2015 The Author(s).)

Background: Meniscus injuries in the United States result in an estimated 850,000 surgical procedures each year. Although meniscectomies are the most commonly performed orthopaedic surgery, little advancement has been made in meniscus replacement and regeneration, and there is currently no total meniscus replacement device approved by the Food and Drug Administration., Hypothesis: A novel fiber-reinforced meniscus scaffold can be used as a functional total meniscus replacement., Study Design: Controlled laboratory study., Methods: A tyrosine-derived, polymer fiber-reinforced collagen sponge meniscus scaffold was evaluated mechanically (tensile and compressive testing) and histologically after 16 and 32 weeks of implantation in an ovine total meniscectomy model (N = 20; 16 implants plus 4 meniscectomies, divided equally over the 2 time periods). The extent of cartilage damage was also measured on tibial plateaus by use of toluidine blue surface staining and on femoral condyles by use of Mankin scores on histological slides., Results: Scaffolds induced formation of neomeniscus tissue that remained intact and functional, with breaking loads approximating 250 N at both 16 and 32 weeks compared with 552 N for native menisci. Tensile stiffness values (99 and 74 N/mm at 16 and 32 weeks, respectively) were also comparable with those of the native meniscus (147 N/mm). The compressive modulus of the neomeniscus tissue (0.33 MPa at both 16 and 32 weeks) was significantly increased compared with unimplanted (time 0) scaffolds (0.15 MPa). There was histological evidence of extensive tissue ingrowth and extracellular matrix deposition, with immunohistochemical evidence of types I and II collagen. Based on significantly decreased surface damage scores as well as Mankin scores, the scaffold implants provided greater protection of articular cartilage compared with the untreated total meniscectomy., Conclusion: This novel fiber-reinforced meniscus scaffold can act as a functional meniscus replacement, with mechanical properties similar to those of the native meniscus, while protecting the articular cartilage of the knee from the extensive damage after a total meniscectomy., Clinical Relevance: This meniscus replacement scaffold has the potential to improve surgical treatment and provide better long-term outcomes for those suffering from severe meniscus damage., (© 2015 The Author(s).)

Background: Current cartilage repair histological scoring systems are unable to explain the relationship between collagen type II deposition and overall repair quality., Purpose/hypothesis: The purpose of this study was to develop a novel zonal collagen type (ZCT) 5-point scoring system to measure chondroinduction in human clinical biopsy specimens collected after marrow stimulation. The hypothesis was that the ZCT scores would correlate with the International Cartilage Repair Society-II (ICRS-II) overall histological repair assessment score and glycosaminoglycan (GAG) content., Study Design: Descriptive laboratory study., Methods: After optimizing safranin O staining for GAG and immunostaining for human collagen type II and type I (Col2 and Col1, respectively), serial sections from clinical osteochondral repair biopsy specimens (13 months after microfracture or microfracture with BST-CarGel; n = 39 patients) were stained and 3 blinded readers performed histomorphometry for percentage of staining, ICRS-II histological scoring, polarized light microscopy (PLM) scoring, and 5-point ZCT scoring based on tidemark morphology, zonal distribution of Col2 and Col1, and Col1 percentage stain. Because 1 biopsy specimen was missing bone, 38 biopsy specimens were evaluated for ICRS-II, PLM, and ZCT scores., Results: Chondroinduction was identified in 21 biopsy specimens as a Col2 matrix fused to bone that spanned the deep-middle-superficial zones ("full-thickness hyaline repair"), deep-middle zones, or deep zone ("stalled hyaline") that was covered with a variable-thickness Col1-positive matrix, and was scored, respectively, as ZCT = 1 (n = 4 biopsy specimens), ZCT = 2 (n = 6) and ZCT = 3 (n = 11). Other biopsy specimens (n = 17) were fibrocartilage (n = 9; ZCT = 4), fibrous tissue (n = 4, ZCT = 5), or non-marrow derived (n = 4; ZCT = 0). Non-marrow derived tissue had a mean mature tidemark score of 84 out of 100 versus a regenerating tidemark score of 24 for all other biopsy specimens (P = .005). Both "stalled hyaline" repair and fibrocartilage had the same mean Col2 percentage stain; however, fibrocartilage was distinguished by heavy Col1 deposits in the deep zone, a 2-fold higher mean Col1 percentage stain (P = .001), and lower surface integrity (P = .03). ZCT scores correlated with GAG content and the ICRS-II overall assessment score, especially when combined with the PLM score for collagen organization (R = 0.82). Histological scores of the deep zone strongly predicted the ICRS-II overall assessment score (R = 0.99)., Conclusion: The ICRS-II overall repair assessment score and GAG content correlated with the extent of Col2 deposition free of fibrosis in the deep/middle zone rather than bulk accumulation of Col2., Clinical Relevance: Biopsy tissue from the BST-CarGel randomized clinical trial (microfracture without and with BST-CarGel, as treatment groups were not unblinded) showed regenerated tissue consistent with a chondroinduction mechanism in at least half of the treated lesions., (© 2015 The Author(s).)

Background: Excessive physiological anterior and rotational knee laxity is thought to be a risk factor for noncontact anterior cruciate ligament (ACL) injuries and inferior reconstruction outcomes, but no thresholds have been established to identify patients with increased laxity., Purpose: (1) To determine if the healthy contralateral knees of ACL-injured patients have greater anterior and rotational knee laxity, leading to different laxity profiles (combination of laxities), compared with healthy control knees and (2) to set a threshold to help discriminate anterior and rotational knee laxity between these groups., Study Design: Case-sectional study; Level of evidence, 3., Methods: A total of 171 healthy contralateral knees of noncontact ACL-injured patients (ACL-H group) and 104 healthy knees of control participants (CTL group) were tested for anterior and rotational laxity. Laxity scores (measurements corrected for sex and body mass) were used to classify knees as hypolax (score <-1), normolax (between -1 and 1), or hyperlax (>1). Proportions of patients in each group were compared using χ(2) tests. Receiver operating characteristic curves were computed to discriminate laxity between the groups. Odds ratios were calculated to determine the probability of being in the ACL-H group., Results: The ACL-H group displayed greater laxity scores for anterior displacement and internal rotation in their uninjured knee compared with the CTL group (P < .05). Laxity profiles were different between the groups for the following associations: normolax in anterior displacement/hypolax in internal rotation (6% [ACL-H] vs 15% [CTL]; P = .02) and hyperlax in anterior displacement/normolax in internal rotation (27% [ACL-H] vs 10% [CTL]; P < .01). The laxity score thresholds were 0.75 for anterior laxity and -0.55 for internal rotation. With both scores above these thresholds, a patient was 3.18-fold more likely to be in the ACL-H group (95% CI, 1.74-5.83)., Conclusion: The healthy contralateral knees of patients with noncontact ACL injuries display different laxity values both for internal rotation and anterior displacement compared with healthy control knees. The identification of knee laxity profiles may be of relevance for primary and secondary prevention programs of noncontact ACL injuries., (© 2015 The Author(s).)

Background: Associated meniscal injury is well recognized at anterior cruciate ligament (ACL) reconstruction, and it is a known risk factor for osteoarthritis., Purpose: To evaluate and characterize the postoperative appearance of articular cartilage after different meniscal treatment in ACL-reconstructed knees using T2 relaxation time evaluation on MRI., Study Design: Cohort study; Level of evidence, 3., Methods: A total of 62 consecutive patients who under ACL reconstruction were recruited in this study, including 23 patients undergoing partial meniscectomy (MS group), 21 patients undergoing meniscal repair (MR group), and 18 patients with intact menisci (MI group) at time of surgery. Clinical evaluation, including subjective functional scores and physical examination, was performed on the same day as the MRI examination and at follow-up times ranging from 2 to 4.2 years. The MRI multiecho sagittal images were segmented to determine the T2 relaxation time value of each meniscus and articular cartilage plate. Differences in each measurement were compared among groups., Results: No patient had joint-line tenderness or reported pain or clicking on McMurray test or instability. There were also no statistically significant differences in functional scores or medial or lateral meniscus T2 values among the 3 groups (P > .05 for both). There was a significantly higher articular cartilage T2 value in the medial femorotibial articular cartilage for the MS group (P < .01) and the MR group (P < .05) compared with that of the MI group, while there was no significant difference in articular cartilage T2 value between the MS and MR groups (P > .05) in each articular cartilage plate. The medial tibial articular cartilage T2 value had a significant positive correlation with medial meniscus T2 value (r = 0.287; P = .024) CONCLUSION: This study demonstrates that knees with meniscectomy or meniscal repair had articular cartilage degeneration at 2 to 4 years postoperatively, with higher articular cartilage T2 relaxation time values compared with the knees with an intact meniscus., (© 2015 The Author(s).)

Background: Meniscal root tears present in many forms and can have profound consequences on the health of knee articular cartilage. While the biomechanics, natural history, and treatment of root tears have been increasingly investigated, the spectrum of meniscal root tear patterns observed during arthroscopic examination has yet to be defined and categorized., Purpose: To establish a classification system for meniscal root tears by reporting the morphology of meniscal root tears from a consecutive series of arthroscopic surgeries. It was hypothesized that meniscal root tears could be grouped into types by distinct tear patterns and that recognition of tear pattern would affect treatment choice., Study Design: Case series; Level of evidence, 4., Methods: All patients who underwent arthroscopic surgery from April 2010 to May 2014 by a single orthopaedic surgeon were included. After arthroscopic examination, data regarding the integrity of the meniscal roots were prospectively recorded in a data registry. Tear morphology and treatment received were subsequently extracted by 2 independent reviewers from operative notes and arthroscopic surgical photos., Results: A total of 71 meniscal root tears in 67 patients were grouped into tear types with similar tear morphologies. Meniscal root tear patterns were categorized into partial stable root tears (type 1; n = 5); complete radial tears within 9 mm of the bony root attachment (type 2; n = 48), further subclassified into types 2A, 2B, and 2C, located 0 to <3 mm, 3 to <6 mm, and 6 to 9 mm from the root attachment, respectively; bucket-handle tears with a complete root detachment (type 3; n = 4); complex oblique tears with complete root detachments extending into the root attachment (type 4; n = 7); and bony avulsion fractures of the root attachments (type 5; n = 7)., Conclusion: This study demonstrated that it was possible to establish a concise classification system to group patients with meniscal root tears by tear morphology. Treatments received varied across tear types., (© 2014 The Author(s).)

Background: The morphometric characteristics of the anterior cruciate ligament (ACL) and the femoral intercondylar notch within which it resides have been implicated as risk factors for injuries to this important stabilizer of the knee. Prior research has produced equivocal results with differing methodologies, and consequently, it is unclear how these characteristics affect the injury risk in male and female patients., Hypothesis: The morphometric characteristics of the ACL and femoral intercondylar notch are individually and independently associated with the risk of suffering a noncontact ACL injury, and these relationships are different in male and female patients., Study Design: Case-control study; Level of evidence, 3., Methods: Magnetic resonance imaging scans of the bilateral knees were obtained on 88 case-control pairs (27 male, 61 female) matched for age, sex, and participation on the same sports team. Patients had suffered a grade III, first-time, noncontact ACL tear. The femoral notch width at 4 locations, the thickness of the bony ridge at the anteromedial outlet of the femoral notch, the femoral notch volume, ACL volume, and ACL cross-sectional area were measured., Results: Multivariate analysis of combined data from male and female patients revealed that decreased ACL volume (odds ratio [OR], 0.829), decreased femoral notch width (OR, 0.700), and increased bony ridge thickness at the anteromedial outlet of the femoral notch (OR, 1.614) were significant independent predictors of an ACL injury. Separate analyses of male and female patients indicated that the femoral notch ridge may be more strongly associated with a risk in female patients, while ACL volume is more strongly associated with a risk in male patients. However, statistical analysis performed with an adjustment for body weight strengthened the association between ACL volume and the risk of injuries in female patients., Conclusion: Morphometric features of both the ACL and femoral notch combine to influence the risk of suffering a noncontact ACL injury. When included together in a multivariate model that adjusts for body weight, the effects of the morphometric measurements are similar in male and female patients. If body weight is not taken into consideration, ACL volume is not associated with a risk in female patients., (© 2014 The Author(s).)

Background: A range of scaffolds is available from various manufacturers for cartilage repair through matrix-associated autologous chondrocyte transplantation (MACT), with good medium- to long-term results., Purpose: To evaluate clinical and magnetic resonance imaging (MRI) outcomes 2 years after MACT on the knee joint using the Novocart 3D scaffold based on a bilayered collagen type I sponge., Study Design: Case series; Level of evidence, 4., Methods: Of 28 initial patients, 23 were clinically and radiologically evaluated 24 months after transplantation. Indications for MACT were chondral or osteochondral lesions on the knee joint with a defect size >2 cm2, no instability, and no malalignment (axis deviation <5°). Then, MRI was performed on a 3-T scanner to assess the magnetic resonance observation of cartilage repair tissue (MOCART) and 3-dimensional (3D) MOCART scores. A variety of subjective scores (International Knee Documentation Committee [IKDC], Knee injury and Osteoarthritis Outcome Score [KOOS], Noyes sports activity rating scale, Tegner activity scale, and visual analog scale [VAS] for pain) were used for clinical evaluation., Results: Two years after MACT, the MRI evaluation showed a mean MOCART score of 73.2 ± 12.4 and a 3D MOCART score of 73.4 ± 9.7. Clinical results showed mean values of 69.8 ± 15.2 for the IKDC; 51.6 ± 21.2, 86.5 ± 13.9, 54.5 ± 23.6, 65.0 ± 8.0, and 91.5 ± 10.6 for the KOOS subscales (Quality of Life, Pain, Sports and Recreation, Symptoms, and Activities of Daily Living, respectively); 77.5 ± 12.7 for the Noyes scale; 4.4 ± 1.6 for the Tegner activity scale; and 1.8 ± 1.7 for the VAS, with statistically significant improvement in all scores other than KOOS-Symptoms., Conclusion: Undergoing MACT using the Novocart 3D scaffold is an applicable method to treat large focal chondral and osteochondral defects, with good short-term clinical and radiological results., (© 2014 The Author(s).)

Background: Randomized controlled trials studying the efficacy and safety of matrix-applied characterized autologous cultured chondrocytes (MACI) versus microfracture (MFX) for treating cartilage defects are limited., Purpose: To compare the clinical efficacy and safety of MACI versus MFX in the treatment of patients with symptomatic cartilage defects of the knee., Study Design: Randomized controlled clinical trial; Level of evidence, 1., Methods: Patients enrolled in the SUMMIT (Demonstrate the Superiority of MACI implant to Microfracture Treatment) trial had ≥1 symptomatic focal cartilage defect (Outerbridge grade III or IV; ≥3 cm(2)) of the femoral condyles or trochlea, with a baseline Knee Injury and Osteoarthritis Outcome Score (KOOS) pain value <55. The co-primary efficacy endpoint was the change in the KOOS pain and function subscores from baseline to 2 years. Histological evaluation and magnetic resonance imaging (MRI) assessments of structural repair tissue, treatment failure, the remaining 3 KOOS subscales, and safety were also assessed., Results: Of the 144 patients treated, 137 (95%) completed the 2-year assessment. Patients had a mean age of 33.8 years and a mean lesion size of 4.8 cm(2). The mean KOOS pain and function subscores from baseline to 2 years were significantly more improved with MACI than with MFX (pain: MACI, 37.0 to 82.5 vs MFX, 35.5 to 70.9; function: MACI, 14.9 to 60.9 vs MFX, 12.6 to 48.7; P = .001). A significant improvement in scores was also observed on the KOOS subscales of activities of daily living (MACI, 43.5 to 87.2 vs MFX, 42.6 to 75.8; P < .001), knee-related quality of life (MACI, 18.8 to 56.2 vs MFX, 17.2 to 47.3; P = .029), and other symptoms (MACI, 48.3 to 83.7 vs MFX, 44.4 to 72.2; P < .001) for patients treated with MACI compared with MFX. Repair tissue quality was good as assessed by histology/MRI, but no difference was shown between treatments. A low number of treatment failures (nonresponders: MACI, 12.5% vs MFX, 31.9%; P = .016) and no unexpected safety findings were reported., Conclusion: The treatment of symptomatic cartilage knee defects ≥3 cm(2) in size using MACI was clinically and statistically significantly better than with MFX, with similar structural repair tissue and safety, in this heterogeneous patient population. Moreover, MACI offers a more efficacious alternative than MFX with a similar safety profile for the treatment of symptomatic articular cartilage defects of the knee., (© 2014 The Author(s).)

Background: Biological repair of cartilage lesions remains a significant clinical challenge because of the lack of natural regeneration and limited treatment options., Hypothesis: Treatment of articular cartilage lesions in the knee with particulated juvenile articular cartilage (PJAC) will result in an improvement in patient symptoms of pain and function and magnetic resonance imaging (MRI) findings at 2 years compared with baseline., Study Design: Case series; Level of evidence, 4., Methods: Patients with symptomatic articular cartilage lesions on the femoral condyles or trochlear groove of the knee were identified for treatment with PJAC. There were 25 patients with a mean age of 37.0 ± 11.1 years and a mean lesion size of 2.7 ± 0.8 cm(2). All patients were assessed preoperatively (baseline) with a knee examination and surveys including the International Knee Documentation Committee (IKDC) subjective knee form, 100-mm visual analog scale (VAS) for pain, and Knee injury and Osteoarthritis Outcome Score (KOOS). Patients were followed at predetermined time points postoperatively through 2 years. Also, MRI was performed at baseline and at 3, 6, 12, and 24 months. At 2 years, patients were given the option of undergoing voluntary diagnostic arthroscopic surgery with cartilage biopsy to assess the histological appearance of the cartilage repair including safranin O staining for proteoglycans and immunostaining for type I and II collagen., Results: Clinical outcomes demonstrated statistically significant increases at 2 years after surgery compared with baseline, with improvements seen as early as 3 months. Over the 24-month follow-up period, the IKDC score increased from a mean of 45.7 to 73.6, KOOS-pain score from 64.1 to 83.7, KOOS-symptoms score from 64.6 to 81.4, KOOS-activities of daily living score from 73.8 to 91.5, KOOS-sports and recreation score from 44.6 to 68.3, and KOOS-quality of life score from 31.8 to 59.9. The MRI results suggested that T2-weighted scores were returning to a level approximating that of normal articular cartilage by 2 years. Histologically, the repair tissue in biopsy samples from 8 patients was composed of a mixture of hyaline and fibrocartilage; immunopositivity for type II collagen was generally higher than for type I collagen, and there appeared to be excellent integration of the transplanted tissue with the surrounding native articular cartilage. Other than elective biopsies, there were no reoperations, although 1 graft delamination was reported at 24 months., Conclusion: This study demonstrates a rapid, safe, and effective treatment for cartilage defects. For the patient population investigated, the clinical outcomes of the PJAC technique showed a significant improvement over baseline, with histologically favorable repair tissue 2 years postoperatively., (© 2014 The Author(s).)

Background: Matrix-assisted autologous chondrocyte transplantation (MACT) was developed to overcome the limitations of first-generation autologous chondrocyte implantation. Although short-term/midterm results are now available for a small series of patients, the literature still lacks studies on large cohorts of patients evaluated at midterm/long-term follow-up., Purpose: Not all patients can have the same benefit from this procedure. The aim of this study is to analyze a large cohort of patients treated with hyaluronan-based MACT to perform clinical profiling and to highlight the patient- and lesion-specific aspects that play a key role in determining the prognosis., Study Design: Case series; Level of evidence, 4., Methods: A total of 142 patients were treated for lesions involving the femoral condyles and trochleae; 133 knees were followed up yearly for 7 years. The average size of the defects was 2.3 ± 1.0 cm2. The origin was traumatic in 44 cases and degenerative in 57 cases, and 32 knees were affected by osteochondritis dissecans (OCD). The clinical outcome was analyzed using the International Knee Documentation Committee (IKDC), EuroQol visual analog scale, and Tegner scores. The influence of the following factors was analyzed: sex, age, body mass index, site, lesion origin, lesion size, previous or combined surgery, and symptom duration., Results: A marked improvement in all scores was found: the IKDC subjective score increased from the basal level of 39.6 ± 14.4 to 71.9 ± 19.8 (P < .0005) at 12 months; a further improvement was observed at 24 months (77.0 ± 20.5; P < .0005). The results were stable over time up to the 7-year evaluation (77.4 ± 22.1). The failure rate was 10.7%. Better results were seen in the trochleae, and among femoral condyles, the following factors were found to influence the clinical outcome positively: traumatic and OCD origin, male sex, short symptom duration (for traumatic lesions), small lesion size (for OCD), young age, and no previous surgery., Conclusion: Treatment with MACT provides good and stable clinical results. Injury origin, sex, symptom duration, lesion size, lesion site, age, and previous surgery might determine the final outcome and can be used as a sort of clinical profiling to guide the surgeon in the choice of this procedure and in giving realistic expectations to patients requiring cartilage treatment.

Background: Meniscus tear patterns in the pediatric population have not been well described., Purpose: To delineate the pattern of meniscus tears and the likelihood of repair at the time of surgery in both children and adolescents., Study Design: Cross-sectional study; Level of evidence, 3., Methods: A retrospective review was performed on all patients between the ages of 10 and 19 years who underwent arthroscopic surgery for a meniscus injury at a single institution. Patients with open growth plates were classified as children, while those with closed growth plates were classified as adolescents. Demographic data were documented, including age, sex, body mass index (BMI), mechanism of injury, and time from injury to surgery. Operative reports and intraoperative photographs were used to assess the tear pattern (type, location, zone) as well as all concomitant procedures and injuries. Tears were classified as discoid, vertical, bucket-handle, radial, oblique, horizontal, fray, root detachment, or complex., Results: Of the 293 patients reviewed, 197 (67%) had lateral meniscus tears, 65 (22%) had medial meniscus tears, and 31 (11%) had tears to both menisci. The cohort was separated into 119 (41%) children (mean age, 13.5 years) and 174 (59%) adolescents (mean age, 16.4 years). Children were more likely to have discoid meniscus tears, lower BMI, and meniscus injuries not associated with ligamentous injuries (P < .05). The rate of associated ligament injuries in children was 28% compared with 51% in adolescents. Overall, the most frequent tear pattern was complex (28%), followed by vertical (16%), discoid (14%), bucket-handle (14%), radial (10%), horizontal (8%), oblique (5%), fray (3%), and root detachment (2%). Complex tears were associated with boys (32% vs 20% in girls; P < .03) and greater mean BMI (27.4 vs 25.1 kg/m(2) in those with noncomplex tears; P < .002), even when taking sex into account. Surgical repair was performed in 47% of all cases (56% in those treated within 3 months of injury vs 42% in those treated after 6 months; P < .03), and there was no difference in the repair rate between the two age groups (49% in children vs 46% in adolescents; P > .05)., Conclusion: Adolescents and children sustain more complex meniscus injuries that are often less repairable than previously reported in the literature. Factors that are associated with greater tear complexity include male sex and obesity. Our findings also suggest that the earlier treatment of meniscus tears may increase the likelihood of repair in younger patients.

Background: Double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) has been reported to yield better joint stability than single-bundle (SB) reconstruction. Few studies have compared the 2 techniques with regard to postoperative articular cartilage changes., Hypothesis: Less cartilage damage should occur in the short term after DB ACLR than after SB ACLR., Study Design: Cohort study; Level of evidence, 2., Methods: The study included 52 patients (27 in the DB group and 25 in the SB group) with no chondral or meniscus injury at primary ACLR, as confirmed under arthroscopy. Four-strand and 6- to 8-strand hamstring autografts, respectively, were used for transtibial SB and 4-tunnel DB reconstruction. Each graft was fixed with an EndoButton bioabsorbable interference screw and a staple. Cartilage status at 6 identified regions was evaluated by second-look arthroscopy and the Outerbridge classification. Other assessments at final follow-up included International Knee Documentation Committee (IKDC) score, Tegner and Lysholm scores, side-to-side difference on KT-2000 arthrometer, and range of motion., Results: The mean time from reconstruction to second-look arthroscopy was 18.2 and 17.3 months for the DB and SB groups, respectively. Both groups had cartilage lesions at the patellofemoral joint (patella, 9 vs 13; trochlea, 5 vs 12) and the medial compartment (1 vs 2). Significantly less severe lesions were found in the DB group than in the SB group (mean grade, 0.33 vs 0.96; P < .05). No significant differences were found between the 2 groups in terms of cartilage status at other regions, IKDC score, Lysholm score, Tegner score, KT-2000 arthrometer anterior laxity, or range of motion., Conclusion: Chondral lesions were found postoperatively in both DB and SB ACLR groups with hamstring autograft. The DB ALCR led to less cartilage damage at the femoral trochlea at short-term follow-up.

Background: Articular cartilage degeneration can develop after anterior cruciate ligament reconstruction (ACLR). Although radiological studies have identified risk factors for the progression of degenerative cartilage changes in the long term, risk factors in the early postoperative period remain to be documented., Hypothesis: Cartilage lesions that are present at surgery progress to cartilage degeneration in the early phase after ACLR., Study Design: Case series; Level of evidence, 4., Methods: T1ρ is the spin-lattice relaxation in the rotating frame magnetic resonance imaging. Sagittal T1ρ maps of the femorotibial joint were obtained before and 1 year after ACLR in 23 patients with ACL injuries. Four regions of interest (ROIs) were placed on images of the cartilage in the medial and lateral femoral condyle (MFC, LFC) and the medial and lateral tibia plateau (MTP, LTP). Changes in the T1ρ value (milliseconds) of each ROI were recorded, and differences between patients with and without cartilage lesions were evaluated. The relationship between changes in the T1ρ value and meniscal tears was also studied., Results: Arthroscopy at ACLR detected cartilage lesions in 15 MFCs, 7 LFCs, and 2 LTPs. The baseline T1ρ value of the MFC and LFC was significantly higher in patients with cartilage lesions (MFC, 40.7 ms; LFC, 42.2 ms) than in patients without cartilage lesions (MFC, 38.0 ms, P = .025; LFC, 39.4 ms, P = .010). At 1-year follow-up, the T1ρ value of the MFC and LFC was also significantly higher in patients with lesions (MFC, 43.1 ms; LFC, 42.7 ms) than in patients without such lesions (MFC, 39.1 ms, P = .002; LFC, 40.4 ms, P = .023, respectively). In patients with cartilage injury, the T1ρ value of the MFC increased during the year after treatment (P = .002). There was no significant difference in the baseline and follow-up T1ρ value in patients with or without meniscal tears on each side although the T1ρ value of the MFC, MTP, and LFC increased during the first year after surgery regardless of the presence or absence of meniscal injuries., Conclusion: Using T1ρ mapping to detect minimal changes, our study demonstrated that cartilage lesions are related to progressive degenerative cartilage changes during the early phase after ACLR.

Background: Osteoarthritis (OA) is a leading cause of pain and disability, and the knee is one of the most commonly affected joints. Many have speculated that injury to the meniscus may play a key role in the development of knee OA; however, the exact relationship of meniscus injury and knee OA is unknown., Purpose: To examine the rate of meniscus injuries in patients with and without incident radiographic knee OA and to explore how the type, size, and location of the meniscus injury affects the development of OA., Study Design: Case-control study; Level of evidence, 3., Methods: A secondary case-control analysis was conducted of the Knee Osteoarthritis Initiative (OAI) database, which is a prospective, longitudinal, multicenter cohort study of knee health in patients at risk for knee OA. Eligible patients included those without radiographic OA at baseline in 1 knee. Thirty-two patients who developed radiographic OA in a previously unaffected knee after 2 years of follow-up were matched to 64 age-, sex-, and body mass index-matched patients who did not develop OA. The study analyzed the relationship between the development of OA and the presence of a meniscus tear or degenerative signal, meniscus extrusion, tear type, and size of injury on the baseline magnetic resonance imaging scans. Conditional logistic regression was used to identify significant predictors of OA., Results: The rate of medial meniscus lesions (tear or degeneration) was not significantly higher in those who developed incident OA (85%) compared with the control patients (68%; P = .07). However, medial meniscus extrusion (odds ratio [OR], 3.03; 95% confidence interval [CI], 1.4-6.5), complex tears (OR, 5.0; 95% CI, 1.0-25), and tears with large radial involvement (OR, 5.92; 95% CI, 1.7-7.5) were more common at baseline in cases compared with controls., Conclusion: Knees with meniscus tears with greater radial involvement and extrusion are at greater risk for later development of radiographic OA.

Background: Magnetic resonance imaging (MRI) is widely used as a preoperative tool to estimate the size of articular cartilage defects to optimize treatment selection. However, the reliability of MRI sizing of cartilage defects is not well understood. Hypothesis/, Purpose: The purpose of this investigation was to compare the size of knee articular cartilage defects on MRI to arthroscopic visualization after debridement. It was hypothesized that MRI sizing would produce measurements that were no different than those made during arthroscopic knee surgery., Study Design: Cohort study (diagnosis); Level of evidence, 2., Methods: Seventy-seven patients (age [mean ± SD], 38 ± 10.7 years) who met inclusion criteria underwent preoperative knee MRI of at least 1.5 T within 1 year of arthroscopic knee surgery for a high-grade cartilage defect. Postdebridement defect sizes were obtained from intraoperative surgery notes and compared with retrospective MRI estimates., Results: Ninety-two total cartilage defects were analyzed with an average of 1.2 high-grade defects per knee and average postdebridement defect area of 2.99 cm(2) per lesion (95% CI, 1.63-2.26 cm(2)). Preoperative MRI analysis estimated a lesion area that was an average of 1.04 cm(2) smaller (95% CI, 0.70-1.39 cm(2); P < .0001). In 74% of the lesions analyzed, defect size was larger on arthroscopic visualization than was estimated by MRI sizing. On average, MRI underestimated the defect area by 70% compared with arthroscopic visualization., Conclusion: Magnetic resonance imaging underestimates the size of articular cartilage defects compared with final postdebridement size as measured during arthroscopic knee surgery. Thus, before arthroscopic surgery, orthopaedic surgeons should consider treatment strategies that are appropriate for a larger defect than predicted by preoperative MRI.

Background: Cartilage repair (CR) procedures are widely accepted for treatment of isolated cartilage defects in the knee joint. However, it is not well known whether these procedures prevent degenerative joint disease., Hypothesis: Cartilage repair procedures prevent accelerated qualitative and quantitative progression of meniscus degeneration in individuals with focal cartilage defects., Study Design: Cohort study; Level of evidence, 2., Methods: Ninety-four subjects were studied. Cartilage repair procedures were performed on 34 patients (osteochondral transplantation, n = 16; microfracture, n = 18); 34 controls were matched. An additional 13 patients received CR and anterior cruciate ligament (ACL) reconstruction (CR&ACL), and 13 patients received only ACL reconstruction. Magnetic resonance imaging at 3.0-tesla with T(1ρ) mapping and sagittal fat-saturated intermediate-weighted fast spin echo (FSE) sequences was performed to quantitatively and qualitatively analyze menisci (Whole-Organ Magnetic Resonance Imaging Score [WORMS] assessment). Patients in the CR and CR&ACL groups were examined 4 months (n = 34; n = 13), 1 year (n = 21; n = 8), and 2 years (n = 9; n = 5) after CR. Control subjects were scanned at baseline and after 1 and 2 years, ACL patients after 1 and 2 years., Results: At baseline, global meniscus T(1ρ) values (mean ± SEM) were higher in individuals with CR (14.2 ± 0.5 ms; P = .004) and in individuals with CR&ACL (17.1 ± 0.9 ms; P < .001) when compared with controls (12.8 ± 0.6 ms). After 2 years, there was a statistical difference between T(1ρ) at the overlying meniscus above cartilage defects (16.4 ± 1.0 ms) and T(1ρ) of the subgroup of control knees without cartilage defects (12.1 ± 0.8 ms; P < .001) and a statistical trend to the CR group (13.3 ± 1.0 ms; P = .09). At baseline, 35% of subjects with CR showed morphological meniscus tears at the overlying meniscus; 10% of CR subjects showed an increase in the WORMS meniscus score within the first year, and none progressed in the second year. Control subjects with (without) cartilage defects showed meniscus tears in 30% (5%) at baseline; 38% (19%) increased within the first year, and 15% (10%) within the second year., Conclusion: This study demonstrated more severe meniscus degeneration after CR surgery compared with controls. However, progression of T(1ρ) values was not observed from 1 to 2 years after surgery. These results suggest that CR may prevent degenerative meniscus changes.

Background: In vivo studies reporting tibial plateau slope as a risk factor for anterior cruciate ligament (ACL) injury have been published with greatly increasing frequency., Purpose: To examine and summarize the in vivo evidence comparing tibial slope in ACL-injured and uninjured populations., Study Design: Systematic review and meta-analysis., Methods: We reviewed publications in Scopus, SPORTDiscus, CINAHL, and PubMed to identify all studies reporting a measure of tibial plateau slope between ACL-injured groups and controls. A meta-analysis was performed including calculation of effect size and 95% confidence interval as well as 95% confidence intervals for the mean values of the measurement in each study., Results: Fourteen studies met our inclusion/exclusion criteria. Five of 6 radiographic studies reporting medial tibial plateau slope (MTPS) demonstrated significant differences between controls and ACL-injured groups, while only 1 of 7 magnetic resonance imaging (MRI) studies reported significant differences between groups. Mean MTPS measurements and standard deviations reported for controls ranged from 2.9° ± 2.8° anterior to 9.5° ± 3° posterior. For ACL-injured patients, MTPS ranged from 1.8° ± 3.5° anterior to 12.1° ± 3.3° posterior. Lateral tibial plateau slope (LTPS) was reported to be significantly greater in ACL-injured groups in all 5 MRI-based studies reporting group comparisons. Mean values for LTPS in controls ranged from 0.3° ± 3.6° anterior slope to 9° ± 4° posterior slope. In ACL-injured groups, mean reported LTPS values ranged from 1.8° ± 3.2° to 11.5° ± 3.54° posterior slope., Conclusion: Despite high measures of reliability for the various methods reported in current studies, there is vast disagreement regarding the actual values of the slope that would be considered "at risk." Reported tibial slope values for control groups vary greatly between studies. In many cases, the study-to-study differences in "normal" tibial slope exceed the difference between controls and ACL-injured patients. The clinical utility of imaging-based measurement methods for the determination of ACL injury risk requires more reliable techniques that demonstrate consistency between studies.

Background: While structured postoperative rehabilitation after matrix-induced autologous chondrocyte implantation (MACI) is considered critical, very little has been made available on how best to progressively increase weightbearing and exercise after surgery., Hypothesis: A significant improvement will exist in clinical and magnetic resonance imaging (MRI)-based scoring measures to 5 years after surgery. Furthermore, there will be no significant differences in outcomes in MACI patients at 5 years when comparing a traditional and an accelerated postoperative weightbearing regimen. Finally, patient demographics, cartilage defect parameters, and injury/surgery history will be associated with graft outcome., Study Design: Randomized controlled trial; level of evidence, 1., Methods: Clinical and radiological outcomes were studied in 70 patients who underwent MACI to the medial or lateral femoral condyle, in conjunction with either an "accelerated" or a "traditional" approach to postoperative weightbearing rehabilitation. Under the accelerated protocol, patients reached full weightbearing at 8 weeks after surgery, compared with 11 weeks for the traditional group. Clinical measures (knee injury and osteoarthritis outcome score [KOOS], short-form health survey [SF-36], visual analog scale [VAS], 6-minute walk test, and knee range of motion) were assessed before surgery and at 3, 6, 12, and 24 months and 5 years after surgery. High-resolution MRI was undertaken at 3, 12, and 24 months and 5 years after surgery and assessed 8 previously defined pertinent parameters of graft repair as well as a combined MRI composite score. The association between clinical and MRI-based outcomes, patient demographics, chondral defect parameters, and injury/surgery history was investigated., Results: Of the 70 patients recruited, 63 (31 accelerated, 32 traditional) underwent clinical follow-up at 5 years; 58 (29 accelerated, 29 traditional) also underwent radiological assessment. A significant time effect (P < .05) was demonstrated for all clinical and MRI-based scores over the 5-year period. While the VAS demonstrated significantly less frequent pain at 5 years in the accelerated group, there were no other significant differences between the 2 groups. Between 24 months and 5 years, a significant improvement (P < .05) in both groups was observed for the sport and recreation subscale of the KOOS as well as a significant decrease (P < .05) in active knee extension for the traditional group. There were no significant differences (P > .05) in the MRI-based scores between 24 months and 5 years after surgery. Patient age and defect size exhibited significant negative correlations (P < .05) with several MRI-based outcomes at 5 years, while there were no significant correlations (P > .05) between clinical and MRI-based outcomes. At 5 years after surgery, 94% and 95% were satisfied with the ability of MACI to relieve their knee pain and improve their ability to undertake daily activities, respectively., Conclusion: The outcomes of this randomized trial demonstrate a safe and effective accelerated rehabilitation protocol as well as a regimen that provides comparable, if not superior, clinical outcomes to patients throughout the postoperative timeline.

Background: Knees undergoing revision anterior cruciate ligament (ACL) reconstruction typically have more intra-articular injuries than do knees undergoing primary reconstruction., Hypothesis: Previous partial meniscectomy (PM) is associated with a higher rate of chondral lesions at revision ACL reconstruction, whereas previous meniscal repair (MR) is not associated with a higher rate of chondral lesions at revision ACL reconstruction, compared with knees undergoing revision ACL with no previous meniscal surgery., Study Design: Cohort study (Prevalence); Level of evidence, 2., Methods: Data from a multicenter cohort was reviewed to determine the history of prior meniscal surgery (PM/MR) and the presence of grade II/III/IV chondral lesions at revision ACL reconstruction. The association between previous meniscal surgery and the incidence of chondral lesions was examined. Patient age was included as a covariate to determine if surgery type contributes predictive information independent of patient age., Results: The cohort included 725 ACL revision surgeries. Chondrosis was associated with patient age (P < .0001) and previous meniscal surgery (P < .0001). After adjusting for patient age, knees with previous PM were more likely to have chondrosis than knees with previous MR (P = .003) or no previous meniscal surgery (P < .0001). There was no difference between knees without previous meniscal surgery and knees with previous MR (P = .7). Previous partial meniscectomy was associated with a higher rate of chondrosis in the same compartment compared with knees without previous meniscal surgery (P < .0001) and knees with previous MR (P ≤ .03)., Conclusion: The status of articular cartilage at the time of revision ACL reconstruction relates to previous meniscal surgery independent of the effect of patient age. Previous partial meniscectomy is associated with a higher incidence of articular cartilage lesions, whereas previous meniscal repair is not. Although this association may reflect underlying differences in the knee at the time of prior surgery, it does suggest that meniscal repair is preferable when possible at the time of ACL reconstruction.

Background: Anterior cruciate ligament (ACL) tears have been implicated in the development of osteoarthritis. Limited data exist on longitudinal follow-up of isolated ACL injury., Hypotheses: All isolated ACL tears are associated with some degree of cartilage injury that will deteriorate over time. There is a threshold of magnetic resonance imaging (MRI)-detectable cartilage injury that will correlate with adverse change in subjective patient-reported outcome measures., Study Design: Cohort study, Level of evidence, 2., Methods: The authors conducted a prospective, observational analysis of 42 knees in 40 patients with acute, isolated ACL injury (14 treated nonoperatively, 28 by reconstruction) with imaging at the time of injury and yearly follow-up for a maximum of 11 years. Morphologic MRI and quantitative T2 mapping was performed with validated outcome measures., Results: All patients sustained chondral damage at initial injury. The adjusted risk of cartilage loss doubled from year 1 for the lateral compartment and medial femoral condyle (MFC) and tripled for the patella. By years 7 to 11, the risk for the lateral femoral condyle was 50 times baseline, 30 times for the patella, and 19 times for the MFC. There was increased risk of cartilage degeneration over the medial tibial plateau (MTP) (P = .047; odds ratio = 6.23; 95% confidence interval [CI], 1.03-37.90) and patella (P = .032; odds ratio = 4.88; 95% CI, 1.14-20.80) in nonsurgical patients compared with surgically treated patients. Size of the bone-marrow edema pattern was associated with cartilage degeneration from baseline to year 3 (P = .001 to .039). Each increase in the MFC Outerbridge score resulted in a 13-point decrease in the International Knee Documentation Committee subjective knee score (P = .0002). Each increase in the MTP resulted in a 2.4-point decrease in the activity rating scale (P = .002)., Conclusion: All patients with acute, traumatic ACL disruption sustained a chondral injury at the time of initial impact with subsequent longitudinal chondral degradation in compartments unaffected by the initial "bone bruise," a process that is accelerated at 5 to 7 years' follow-up.

Background: Characterized chondrocyte implantation (CCI) results in significantly better early structural tissue regeneration than microfracture (MF), and CCI has a midterm clinical benefit over microfracture., Purpose: This study was undertaken to evaluate the 5-year clinical outcome of CCI in a randomized comparison with MF for the treatment of symptomatic cartilage defects of the femoral condyles of the knee., Study Design: Randomized controlled trial; Level of evidence, 1., Methods: Participants aged 18 to 50 years with a symptomatic isolated International Cartilage Repair Society (ICRS) grade III or IV cartilage lesion of the femoral condyles between 1 and 5 cm(2) were randomized to either CCI or MF. Clinical outcomes were measured up to 60 months after surgery using the Knee Injury and Osteoarthritis Outcome Score (KOOS). The main outcome parameter was change from baseline in overall KOOS (oKOOS). Adverse events were monitored., Results: Fifty-one participants were treated with CCI and 61 with MF. On average, clinical benefit was maintained through the 60-month follow-up period. The average change from baseline in oKOOS was not different between both groups (least squares [LS] mean ± standard error [SE] 18.84 ± 3.58 for CCI vs 13.21 ± 5.63 for MF; P = .116). Treatment failures were comparable (n = 7 in CCI vs n = 10 in MF), although MF failures tended to occur earlier. Subgroup analysis revealed that CCI resulted in better outcome in participants with time since symptom onset of less than 3 years, which was statistically significant and clinically relevant (change in oKOOS <3 years mean ± SE 25.96 ± 3.45 for CCI vs 15.28 ± 3.17 for MF; P = .026 vs oKOOS >3 years mean ± SE 13.09 ± 4.78 for CCI vs 17.02 ± 4.50 for MF, P = .554). Other subgroup analyses such as age (cutoff 35 years) did not show a difference. Female patients showed more failures irrespective of treatment., Conclusion: At 5 years after treatment, clinical outcomes for CCI and MF were comparable. In the early treatment group, CCI obtained statistically significant and clinically relevant better results than MF. Delayed treatment resulted in less predictable outcomes for CCI. These results provide strong evidence that time since onset of symptoms is an essential variable that should be taken into account in future treatment algorithms for cartilage repair of the knee.

Background: The long-term radiographic and subjective results of patients with posterior lateral meniscus root tears left in situ at the time of anterior cruciate ligament reconstruction has not been reported., Hypothesis: The authors hypothesized that patients who had posterior lateral meniscus root tears left in situ would have statistically significantly lower subjective scores and greater joint-space narrowing as compared with a control group., Study Design: Cohort study; Level of evidence, 3., Methods: Thirty-three patients who had isolated posterior lateral meniscus root tear and >5 years objective and subjective follow-up were evaluated and compared with a matched control group without meniscal tears based on sex, chronicity of tear, age, and follow-up time. Patients were evaluated subjectively and objectively using the International Knee Documentation Committee criteria., Results: The mean objective follow-up time was 10.6 ± 4.5 years. The mean subjective total score was 84.6 ± 14 in the study group versus 90.5 ± 13 in the control group (P = .09). Radiographs showed lateral joint-space narrowing rated as normal in 19, mild in 10, moderate in 3, and severe in 1 versus the control group, which was normal in 28 and mild in 5 patients. The measured amount of lateral joint-space narrowing compared with the other knee was 1.0 ± 1.6 mm in the study group versus 0 ± 1.1 mm in the controls on 45° flexed posteroanterior radiographs (P < .006)., Conclusion: At a mean of 10 years' follow-up of posterior lateral meniscus root tears left in situ, mild lateral joint-space narrowing was measured without significant differences in subjective or objective scores compared with controls. This study provides a baseline that can be used to compare the results of procedures used to treat these tears in other manners.

Injury to the posteromedial corner (PMC) of the knee differs anatomically and biomechanically from isolated injury to the medial collateral ligament. Newer anatomic and biomechanical studies are refining the field's understanding of the medial side of the knee, as well as its role in multiple ligament injuries. Valgus instability places additional strain on a reconstructed anterior or posterior cruciate ligament, which can contribute to late graft failure. Injuries to the PMC may not heal without surgical repair or reconstruction, particularly when part of a multiple-ligament injury. Identification of PMC injury before cruciate reconstruction is important so that appropriate repair or reconstruction of the PMC and medial collateral ligament can be undertaken at the same time. This article reviews the relevant literature on the PMC, discusses reasons for selective operative management, and illustrates reconstructive strategies for PMC injuries occurring as part of a medial-sided or multiligament injury to the knee.

Background: A double-network (DN) gel, which was composed of poly-(2-acrylamido-2-methylpropanesulfonic acid) and poly-(N,N'-dimetyl acrylamide) (PAMPS/PDMAAm), has the potential to induce chondrogenesis both in vitro and in vivo., Purpose: To establish the efficacy of a therapeutic strategy for an articular cartilage defect using a DN gel., Study Design: Controlled laboratory study., Methods: A 4.3-mm-diameter osteochondral defect was created in rabbit trochlea. A DN gel plug was implanted into the defect of the right knee so that a defect 2 mm in depth remained after surgery. An untreated defect of the left knee provided control data. The osteochondral defects created were examined by histological and immunohistochemical evaluations, surface assessment using confocal laser scanning microscopy, and real-time polymerase chain reaction (PCR) analysis at 4 and 12 weeks. Samples were quantitatively evaluated with 2 scoring systems reported by Wayne et al and O'Driscoll et al., Results: The DN gel-implanted defect was filled with a sufficient volume of the hyaline cartilage tissue rich in proteoglycan and type 2 collagen. Quantitative evaluation using the grading scales revealed a significantly higher score in the DN gel-implanted defects compared with the untreated control at each period (P < .0001). The mean relative values of type 2 collagen mRNAs in the regenerated tissue were obviously higher in the DN gel-implanted defect than in the untreated control at each period. The mean surface roughness of the untreated control was significantly higher than the normal cartilage at 12 weeks (P = .0106), while there was no statistical difference between the DN gel-implanted and normal knees., Conclusion: This study using the mature rabbit femoral trochlea osteochondral defect model demonstrated that DN gel implantation is an effective treatment to induce cartilage regeneration in vivo without any cultured cells or mammalian-derived scaffolds., Clinical Relevance: This study has prompted us to develop a potential innovative strategy to repair cartilage lesions in the field of joint surgery.

Background: The authors developed a novel technique to improve tendon-bone attachment by hybridizing calcium phosphate with a tendon graft using an alternate soaking process. However, the long-term result is unclear regarding the function of the anterior cruciate ligament–reconstructed knee and the interface between the tendon and the bone., Purpose: To clarify the effects of the calcium phosphate–hybridized tendon graft by analyzing the biomechanical behavior of the reconstructed knee, bone tunnel wall, and interface between the tendon and the bone, compared with the untreated knee at 1 year in goats., Study Design: Controlled laboratory study., Methods: The authors analyzed knee kinematics and in situ forces in a replacement graft, as well as computed tomography for new bone formation in the bone tunnel and histology of the tendon-bone interface, with and without the calcium phosphate-hybridized tendon graft., Results: In the calcium phosphate group, the anteroposterior translations in the reconstructed knees were shorter and the corresponding in situ forces greater than those in the control group at full extension and 60° of knee flexion. The in situ force in response to applied internal tibial torques in the calcium phosphate group at full extension was greater than that in the control group. More new bone formation in the bone tunnel and cartilage layer between the tendon-bone interface at the joint aperture site of the calcium phosphate group was observed than in the control group., Conclusion: The calcium phosphate–hybridized tendon graft promotes knee stability because of the firm tendon-bone healing with cartilage layer and new bone formation., Clinical Relevance: Anterior cruciate ligament reconstruction using the calcium phosphate–hybridized tendon graft may lead to good long-term outcomes.

Background: The availability remains limited of midterm clinical and radiologic results into matrix-induced autologous chondrocyte implantation (MACI). Outcomes are required to validate the efficacy of MACI as a suitable surgical treatment option for articular cartilage defects in the knee., Hypothesis: A significant improvement in clinical and magnetic resonance imaging-based (MRI-based) outcomes after MACI will exist throughout the postoperative timeline to 5 years after surgery. Furthermore, patient demographics, cartilage defect parameters, and injury/surgery history will be associated with patient and graft outcome, whereas a significant correlation will exist between clinical and MRI-based outcomes at 5 years after surgery., Study Design: Case series; Level of evidence, 4., Methods: A prospective evaluation was undertaken to assess clinical and MRI-based outcomes to 5 years in 41 patients (53 grafts) after MACI to the knee. After MACI surgery and a 12-week structured rehabilitation program, patients underwent clinical assessments (Knee injury and Osteoarthritis Outcome Score, SF-36, 6-minute walk test, knee range of motion) and MRI assessments at 3, 12, and 24 months, as well as 5 years after surgery. The MRI evaluation assessed 8 previously defined pertinent parameters of graft repair, as well as a combined MRI composite score., Results: A significant improvement (P < .05) was demonstrated for all Knee injury and Osteoarthritis Outcome Score and SF-36 subscales over the postoperative timeline, as well as the 6-minute walk test and active knee extension. A significant improvement (P < .0001) was observed for the MRI composite score, as well as several individual graft scoring parameters. At 5 years after surgery, 67% of MACI grafts demonstrated complete infill, whereas 89% demonstrated good to excellent filling of the chondral defect. Patient demographics, cartilage defect parameters, and injury/surgery history demonstrated no significant pertinent correlations with clinical or MRI-based outcomes at 5 years, and no significant correlations existed between clinical and MRI-based outcome measures. At 5 years after surgery, 98% of patients were satisfied with the ability of MACI surgery to relieve knee pain; 86%, with improvement in their ability to perform normal daily tasks; and 73%, with their ability to participate in sport 5 years after MACI., Conclusion: These results suggest that MACI provides a suitable midterm treatment option for articular cartilage defects in the knee. Long-term follow-up is essential to confirm whether the repair tissue has the durability required to maintain long-term patient quality of life.

Background: Lubricin and hyaluronic acid lubricate articular cartilage and prevent wear. Because lubricin loss occurs after anterior cruciate ligament injury, intra-articular lubricin injections may reduce cartilage damage in the anterior cruciate ligament-deficient knee., Purpose: This study was conducted to determine if lubricin and/or hyaluronic acid supplementation will reduce cartilage damage in the anterior cruciate ligament-deficient knee., Study Design: Controlled laboratory study., Methods: Thirty-six male rats, 3 months old, underwent unilateral anterior cruciate ligament transection. They were randomized to 4 treatments: (1) saline (phosphate-buffered saline [PBS]), (2) hyaluronic acid (HA), (3) purified human lubricin (LUB), and (4) LUB and HA (LUB+HA). Intra-articular injections were given twice weekly for 4 weeks starting 1 week after surgery. Knees were harvested 1 week after the final injection. Radiographs of each limb and synovial fluid lavages were obtained at harvest. Histologic analysis was performed to assess cartilage damage using safranin O/fast green staining. Radiographs were scored for the severity of joint degeneration using the modified Kellgren-Lawrence scale. Synovial fluid levels of sulfated glycosaminoglycan, collagen II breakdown, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and lubricin were measured using enzyme-linked immunosorbent assay (ELISA)., Results: Treatment with LUB or LUB+HA significantly decreased radiographic and histologic scores of cartilage damage (P = .039 and P = .015, respectively) when compared with the PBS and HA conditions. There was no evidence of an effect of HA nor was the LUB effect HA-dependent, suggesting that the addition of HA did not further reduce damage. The synovial fluid of knees treated with LUB had significantly more lubricin in the synovial fluid at euthanasia, although there were no differences in the other cartilage metabolism biomarkers., Conclusion: Supplemental intra-articular LUB reduced cartilage damage in the anterior cruciate ligament-transected rat knee 6 weeks after injury, while treatment with HA did not., Clinical Relevance: Although longer term studies are needed, intra-articular supplementation (tribosupplementation) with lubricin after anterior cruciate ligament injury may protect the articular cartilage in the anterior cruciate ligament-injured knee.

Background: Meniscus allograft transplantation (MAT) is useful for meniscus-deficient knees. Although meniscal extrusion is common after MAT, there is no consensus regarding the criteria for normal meniscal extrusion or the relationship between clinical and radiologic results., Hypothesis: Meniscal extrusion after MAT results in poor clinical, radiologic, and arthroscopic outcomes., Study Design: Case series; Level of evidence, 4., Methods: Thirty-six of 60 patients undergoing MAT from September 2002 to June 2007 who were available for follow-up evaluation for more than 2 years were evaluated. The study population (31 men, 5 women) consisted of 15 and 21 cases of medial and lateral meniscus transplant, respectively. Knee status was evaluated by Lysholm score, plain radiography, and magnetic resonance imaging preoperatively and postoperatively. Second-look examinations were performed in 18 cases., Results: Mean follow-up was 31.4 months (range, 24-36). Lysholm knee score increased significantly (mean, 88.2; range, 70-100) on final visit versus the preoperative value (mean, 61.2; range, 26-83; P < .001). Joint-space narrowing was 0.08 mm (range, -2.58 to 1.92) in extension AP and -0.09 mm (range, -2.3 to 1.8) in Rosenberg view. Kellgren-Lawrence arthrosis grade did not change in 28 knees (77.8%) and progressed by 1 grade in 8 knees. Meniscal extrusion extent was 3.87 ± 1.94 mm and relative percentage extrusion was 42.1% ± 17.7%. Seven cases (19.4%) showed minor extrusion (<3 mm), 27 (75%) showed major extrusion (>3 mm), and 2 (5.6%) showed no extrusion. Further degeneration was absent in 28 knees (77.8%) on magnetic resonance imaging. In second-look arthroscopic examinations at an average of 26.3 months, 11 of 18 (63.6%) cases showed no progression of cartilage degeneration. There was no significant correlation between meniscal extrusion and other parameters., Conclusion: This study indicated that MAT can improve the clinical status of the meniscectomized knee. Although meniscal extrusion occurred after surgery in most cases, there was no significant correlation with various clinical, radiologic, or arthroscopic outcomes. Further studies are required to evaluate long-term effects of meniscal extrusion.

Background: The International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form (IKDC Knee Form) is a valid, reliable, and responsive measure of knee-related symptoms, function, and sports activities in adults. Despite the incidence of knee injuries in younger individuals, the measurement characteristics of the IKDC Knee Form have not been established. Hypothesis/, Purpose: The purpose of this study was to investigate the validity and internal consistency of the IKDC Knee Form in pediatric, adolescent, and young adult patients with a variety of knee conditions. The authors hypothesized that the IKDC Knee Form would be a valid and consistent measure of knee function in these age groups., Study Design: Cohort study (diagnosis); Level of evidence, 2., Methods: The IKDC Knee Form and Pediatric Quality of Life Inventory 4.0 Generic Core Scales (PedsQL) physical functioning component were administered to 673 individuals between 6 and 18 years of age. The internal consistency and validity of the IKDC Knee Form were determined for the entire cohort and for age group cohorts (pediatric, 6-12 years; adolescent, 13-15 years; young adult, 16-18 years) using the PedsQL physical functioning component for comparison., Results: The results were similar across all age groups. In the original format, internal consistency was high and factor analysis showed a single, dominant component underlying the item responses for each age group. Items 2, 3, and 6 may contribute to measurement error in young individuals. Correlation between the IKDC Knee Form and PedsQL physical functioning component score was moderately high for the entire cohort (r = .83) and for all age groups (pediatric, r = .84; adolescent, r = .84; young adult, r = .79)., Conclusion: In its current form, the IKDC Knee Form is a valid and consistent knee-specific measure of symptoms, function, and sports activity in individuals between the ages of 6 and 18 years with a variety of knee problems. Further work is needed to establish the reliability and responsiveness of the IKDC Knee Form for this age group.

Background: Increased knee pain at the time of anterior cruciate ligament reconstruction may potentially predict more difficult rehabilitation, prolonged recovery, and/or be predictive of increased knee pain at 2 years., Hypothesis: A bone bruise and/or other preoperative factors are associated with more knee pain/symptoms at the time of index anterior cruciate ligament reconstruction, and the presence of a bone bruise would be associated with specific demographic and injury-related factors., Study Design: Cohort study (prevalence); Level of evidence, 2., Methods: In 2007, the Multicenter Orthopaedic Outcomes Network (MOON) database began to prospectively collect surgeon-reported magnetic resonance imaging bone bruise status. A multivariable analysis was performed to (1) determine if a bone bruise, among other preoperative factors, is associated with more knee symptoms/pain and (2) examine the association of factors related to bone bruise. To evaluate the association of a bone bruise with knee pain/symptoms, linear multiple regression models were fit using the continuous scores of the Knee injury and Osteoarthritis Outcome Score (KOOS) symptoms and pain subscales and the Short Form 36 (SF-36) bodily pain subscale as dependent variables. To examine the association between a bone bruise and risk factors, a logistic regression model was used, in which the dependent variable was the presence or absence of a bone bruise., Results: Baseline data for 525 patients were used for analysis, and a bone bruise was present in 419 (80%). The cohort comprises 58% male patients, with a median age of 23 years. The median Marx activity level was 13. Factors associated with more pain were higher body mass index (P < .0001), female sex (P = .001), lateral collateral ligament injury (P = .012), and older age (P = .038). Factors associated with more symptoms were a concomitant lateral collateral ligament injury (P = .014), higher body mass index (P < .0001), and female sex (P < .0001). Bone bruise is not associated with symptoms/pain at the time of index anterior cruciate ligament reconstruction. None of the factors included in the SF-36 bodily pain model were found to be significant. After controlling for other baseline factors, the following factors were associated with a bone bruise: younger age (P = .034) and not jumping at the time of injury (P = .006)., Conclusion: After anterior cruciate ligament injury, risk factors associated with a bone bruise are younger age and not jumping at the time of injury. Bone bruise is not associated with symptoms/pain at the time of index anterior cruciate ligament reconstruction.

Background: Although several devices for meniscal repairs have become available, a successful outcome is ultimately due to a healed meniscus on the clinical findings. The authors assessed the repair integrity after meniscal repair with the FasT-Fix device using second-look arthroscopy., Hypothesis: Meniscal repair with the FasT-Fix will lead to arthroscopically evident healing, but some menisci will show incomplete healing even in clinically successful cases and have newly formed injuries on the meniscal substance resulting from the path of the implant., Study Design: Case series; Level of evidence, 4., Methods: Sixty-five consecutive patients were studied, in whom 84 menisci were subjected to all-inside meniscal repair with the FasT-Fix device in conjunction with anterior cruciate ligament reconstruction. Repair was only performed on longitudinal or double longitudinal tears within the red-red or red-white zone. The repaired menisci were evaluated by second-look arthroscopy at the time of staged hardware removal after anterior cruciate ligament reconstruction., Results: Sixty-two meniscal tears in 46 patients were available for this study. Eight patients were found to be symptomatic and considered to be clinical failures. The clinical success rate was 83%. At second-look arthroscopy, 46 tears (74%) were healed, 9 (15%) were healed incompletely, and 7 (11%) had failed. In the failed menisci, 1 had meniscal symptoms, while the other 6 were asymptomatic. In the 9 menisci with incomplete healing, 3 were associated with nonspecific knee pain but none showed meniscal symptoms. Newly formed injuries, which occurred in an area different from the original repair site, were confirmed on the surface of 19 menisci (35%) among the healed and incompletely healed menisci. Thirty menisci (48%) displayed successful and complete healing of the original tear site without newly formed tears., Conclusion: Meniscal repair with the FasT-Fix in conjunction with anterior cruciate ligament reconstruction resulted in complete healing in 74% of cases. Eighty-three percent of menisci were symptom-free regardless of meniscal integrity. Even when the menisci repaired are asymptomatic and considered to be a clinical success, however, there may be newly formed injuries.

Background: In osteochondral defects, subchondral bone, as a load-bearing structure, is believed to be important for bone and cartilage regeneration., Hypothesis: A stiff scaffold creates better conditions for bone formation and cartilage regeneration than does a softer one., Study Design: Controlled laboratory study., Methods: Critical osteochondral defects were created in the femoral condyles of 24 sheep. Subchondral bone was reconstructed with a stiff scaffold or a modified softer one, with untreated defects serving as controls. The repair response was evaluated with mechanical, histological, and histomorphometrical techniques at 3 and 6 months postoperatively., Results: The elastic modulus of regenerated fibrocartilage over the stiff scaffold tended to be higher than in the soft scaffold group (61% vs 46% of healthy cartilage) at 3 months. No difference was determined at 6 months; all were well below healthy cartilage. Treated defects showed substantial degradation of the soft scaffold with surrounding sclerotic bone at 3 and 6 months. In contrast, degradation of the stiff scaffold was slower and occurred together with continuous osseous replacement., Conclusion: Stiff scaffolds were found to improve bone regeneration. In contrast, soft scaffolds provided less support, and consequently subchondral bone became sclerotic. Although regenerated cartilage formed over the stiff scaffolds at 3 months, and these exhibited better mechanical properties than did the soft scaffold group, the mechanical properties in both treated groups were the same at 6 months, not dissimilar to that of tissue formed in the untreated specimens and inferior to native articular cartilage., Clinical Relevance: The results imply that subchondral defect filling in clinical settings advances bone regeneration and should have a comparable stiffness to that of healthy subchondral bone rather than being too flexible. Degradation of resorbable materials and consequently the loss of stiffness may compromise the healing of critical defects.

Background: The knee is one of the most frequently injured joints, including 80 000 anterior cruciate ligament (ACL) tears in the United States each year. Bone bruises are seen in over 80% of patients with ACL injuries, and have been associated with an overt loss of cartilage overlying those regions within 6 months of injury., Hypothesis: The level of contact pressure developed in the human knee joint and the extent of articular cartilage and underlying subchondral bone injuries will depend on the mechanism of applied loads/moments during rupture of the ACL., Study Design: Controlled laboratory study., Methods: Seven knee pairs, flexed to 30 degrees , were loaded in compression or internal torsion until injury. Pressure-sensitive film recorded the magnitude and location of contact. Histologic analysis and magnetic resonance imaging were used to document microtrauma to the tibial plateau cartilage and subchondral bone., Results: All specimens suffered ACL injury, either in the form of a midsubstance rupture or avulsion fracture. The contact area and pressures were higher for compression than torsion experiments. After being loaded, the articular cartilage in the central and posterior regions of the medial tibial plateau showed increased magnetic resonance imaging signal intensity, corresponding to an increased susceptibility to absorb water. Histologically, there were more microcracks in the subchondral bone and more articular cartilage damage in the compression than torsion experiments., Conclusion: Significant damage occurs to the articular cartilage and underlying subchondral bone during rupture of the ACL. The types and extent of these tissue injuries are a function of the mechanism of ACL rupture., Clinical Relevance: Patients suffering an ACL injury may be at risk of osteochondral damage, especially if the mechanism of injury involves a high compressive loading component, such as during a jump landing.

Background: The quality of tendons has considerable limitations regarding torn rotator cuff tendons. Tissue-engineering techniques using a biodegradable scaffold offer potential alternatives for recreating a valid tendon-to-bone interface., Hypothesis: A polyglycolic acid (PGA) sheet could facilitate the regeneration of the rotator cuff tendon insertion in vivo., Study Design: Controlled laboratory study., Methods: An implant consisting of a PGA sheet, a rapidly absorbable material, was used to replace a completely resected infra-spinatus tendon insertion in 33 adult Japanese white rabbits. The contralateral infraspinatus tendon was replaced by poly-L-lactate-epsilon-caprolactone (PLC), a slowly absorbable material, by the same methods based on the results of the pilot study. Histological comparisons were made at 4, 8, and 16 weeks, and mechanical evaluations were performed at 4 and 16 weeks in both groups. Unrepaired defects were created in a control group., Results: In the control group, the rotator cuff defects were covered with thin fibrous membranes with many fibroblasts arranged in an irregular pattern. In the PLC group, some chondrocytes were seen in the tendon insertion; however, these were not arranged along the long axis for a 16-week period. In the PGA group, a well-arranged fibrocartilage layer could be found in the regenerated tendon insertions; however, these tendon insertions were mainly regenerated by type III collagen. In mechanical examinations, the PGA group had significantly higher values in the maximum failure load, tensile strength, and Young's modulus for the 4-week and 16-week periods. These 3 categories statistically improved from 4 to 16 weeks postoperatively in both groups except for the Young's modulus in the PGA group (E = 5.66 at 4 weeks to 5.53 at 16 weeks)., Conclusion: The PGA sheet scaffold material allows for tendon insertion regeneration with a fibrocartilage layer but displays mechanical properties inferior to those of the normal tendon in an animal model., Clinical Relevance: The PGA sheet represent a possible alternative scaffold material for tendon regeneration in rotator cuff repair.

Background: Anterior cruciate ligament (ACL) injury incurred from high-impact activities leads to an increased risk of osteoarthritis., Hypothesis: Impact forces that cause ACL failure can also inflict cartilage damage, whereby its extent and distribution may be influenced by the ligament failure mechanism., Study Design: Descriptive laboratory study., Methods: Six porcine knee specimens were mounted to a material testing system at 70 degrees of flexion. During compression, rotational and translational data of the specimens were recorded with a motion-capture system. Compression was successively repeated with increasing actuator displacement until a significant drop in compressive force response was observed; ligament failure was assessed by dissection. Osteocartilage explants were extracted from the meniscus-covered sites (anterior, exterior, and posterior) and exposed (interior) sites on both tibial compartments. The explants were sectioned, stained, and histologically scored using the modified Mankin grading system., Results: Five of the 6 specimens incurred ACL failure. On failure, a significant compressive force drop (1812.5-2659.3 N) was observed together with considerable posterior femoral translation; 2 specimens underwent external rotation, while 2 had internal rotation and 1 had no substantial rotation. Generally, the meniscus-covered sites displayed significant surface fraying and occasional deep clefts; the exposed site did not present substantial surface irregularities but indicated more tidemark disruption. Higher Mankin scores observed at certain sites illustrated a localized presence of contact and shear forces, which may be caused by pivoting and sliding of the femoral condyles during rotation., Conclusion: The porcine model can be a tenable preliminary option for assessing the role of the human ACL during joint compression. Impact loads that result in ligament failure can potentially inflict considerable cartilage damage; the damage profile may be affected by the type of failure mechanism., Clinical Relevance: Cartilage injury arising at the time of ACL injury may lead to an accelerated risk of joint degeneration.

Background: Knee hyperextension can be a serious and disabling injury in both the athletic and general patient population. Understanding the pathoanatomy and pathomechanics is critical for accurate surgical soft tissue reconstructions., Purpose: To quantify the effects of knee hyperextension injury on knee laxity in a human cadaveric model and to qualitatively assess the anatomical injury pattern through surgical dissection., Study Design: Descriptive laboratory study., Methods: Six fresh-frozen cadaveric knees were rigidly mounted on a custom knee testing system that simulates clinical laxity tests. The knee laxity measurements consisted of anterior-posterior laxity, internal-external rotational laxity, and varus-valgus laxity using a custom testing setup and a Microscribe 3DLX system. The laxity data were collected at both 30 degrees and 90 degrees of knee flexion for the intact specimens and then after 15 degrees and 30 degrees hyperextension injury. After biomechanical assessment, a detailed dissection was performed to document the injured structures in the knee. Repeated-measures analysis of variance with a Tukey post hoc test (P < .05) was used for statistical comparison., Results: The results from this study suggest progressive damage to translational and rotational knee soft-tissue restraints with increasing knee hyperextension. Knee hyperextension to 30 degrees caused the most significant increase in anterior-posterior and rotational laxity. Anatomical dissections showed a general injury pattern to the posterolateral corner, partial femoral anterior cruciate ligament avulsion in 4 of 6 specimens, and no gross posterior cruciate ligament injuries., Conclusion: Injuries to the posterolateral corner of the knee can result from isolated knee hyperextension., Clinical Relevance: The clinician should be aware of the potential for posterolateral corner injuries with isolated knee hyperextension. This will allow early surgical planning and primary surgical repair.

Background: The pathogenesis of tendon overuse injuries is poorly understood. The histopathology underlying tendinopathy at various anatomical locations is similar and may reflect a common pathologic process., Hypothesis: Apoptosis contributes to the pathophysiology in patellar tendinopathy., Study Design: Case control study; Level of evidence, 3., Methods: We compared biopsy specimens from the patellar tendon in patients with patellar tendinopathy diagnosed clinically and with typical magnetic resonance image findings with biopsy specimens from a control group without any previous or current knee complaints to suggest patellar tendinopathy. The presence of apoptosis was examined with immunohistochemical methods using a polyclonal antibody recognizing active caspase-3, confirmed by labeling DNA strand breaks (F7-26 antibody) and nuclear morphology (fragmentation and condensation)., Results: The number of apoptotic cells per unit area (4.5 mm(2)) was 0.91 +/- 0.81 (SD) in tendinopathic samples and 0.21 +/- 0.21 in controls (P = .026). Although the tendinopathic samples displayed increased cellularity (average 162.5 nuclei/mm(2) vs 98.9 nuclei/mm(2)), the apoptotic index was higher (0.42% vs 0.17%, P = .014)., Conclusion: Increased apoptotic cell death is a feature of patellar tendinosis. The role of apoptosis within the broader framework and time course of tendon overuse injury remains to be established.