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Background: Animal models have long been considered an important modality for studying ACL injuries. However, to our knowledge, the value of these preclinical models to study sex-related phenomena associated with ACL injury and recovery has not been evaluated., Questions/purposes: We asked whether (1) prominent anatomic and (2) biomechanical factors differ between female and male porcine knees, particularly those known to increase the risk of ACL injury., Methods: Eighteen intact minipig knees (nine males, nine females) underwent MRI to determine the femoral bicondylar width, intercondylar notch size (width, area and index), medial and lateral tibial slope, ACL size (length, cross-sectional area, and volume), and medial compartment tibiofemoral cartilage thickness. AP knee laxity at 30°, 60°, and 90° flexion and ACL tensile structural properties were measured using custom-designed loading fixtures in a universal tensile testing apparatus. Comparisons between males and females were performed for all anatomic and biomechanical measures. The findings then were compared with published data from human knees., Results: Female pigs had smaller bicondylar widths (2.9 mm, ratio=0.93, effect size=-1.5) and intercondylar notches (width: 2.0 mm, ratio=0.79, effect size=-2.8; area: 30.8 mm2, ratio=0.76, effect size=-2.1; index: 0.4, ratio=0.84, effect size=-2.0), steeper lateral tibial slope (4.3°, ratio=1.13, effect size=1.1), smaller ACL (length: 2.7 mm, ratio=0.91, effect size=-1.1; area: 6.8 mm2, ratio=0.74, effect size=-1.5; volume: 266.2 mm3, ratio=0.68, effect size=-1.5), thinner medial femoral cartilage (0.4 mm, ratio=0.8, effect size=-1.1), lower ACL yield load (275 N, ratio=0.81, effect size=-1.1), and greater AP knee laxity at 30° (0.7 mm, ratio=1.32, effect size=1.1) and 90° (0.5 mm, ratio=1.24, effect size=1.1) flexion compared with their male counterparts. These differences were significant for all parameters (p≤0.04). Observed sex-related differences were similar to those reported for the human knee., Conclusions: Significant differences exist between knees of male and female pigs with respect to prominent anatomic and biomechanical factors. Our findings strongly agreed with published data regarding human knees., Clinical Relevance: The findings highlight the use of the porcine large animal model to study the role of sex on ACL injuries and surgical outcome. This validated preclinical model may facilitate the development of novel, sex-specific interventions to prevent and treat ACL injuries for male and female patients.

Background: Although relatively uncommon, spontaneous healing from a meniscus injury has been observed even within the avascular area. This may be the result of the existence of mesenchymal stem cells in synovial fluid., Questions/purposes: The purpose of this study was to investigate whether mesenchymal stem cells existed in the synovial fluid of the knee after meniscus injury., Methods: Synovial fluid was obtained from the knees of 22 patients with meniscus injury just before meniscus surgery and from 8 volunteers who had no history of knee injury. The cellular fraction of the synovial fluid was cultured for 14 days followed by analysis for multilineage potential and presentation of surface antigens characteristic of mesenchymal stem cells. Colony-forming efficiency and proliferation potential were also compared between the two groups., Results: Cells with characteristics of mesenchymal stem cells were observed in the synovial fluid of injured knees to a much greater degree than in uninjured knees. The colony-forming cells derived from the synovial fluid of the knee with meniscus injury had multipotentiality and surface epitopes identical to mesenchymal stem cells. The average number of colony formation, obtained from 1 mL of synovial fluid, in meniscus-injured knees was 250, higher than that from healthy volunteers, which was 0.5 (p < 0.001). Total colony number per synovial fluid volume was positively correlated with the postinjury period (r = 0.77, p < 0.001)., Conclusions: Mesenchymal stem cells were found to exist in synovial fluid from knees after meniscus injury. Mesenchymal stem cells were present in higher numbers in synovial fluid with meniscus injury than in normal knees. Total colony number per synovial fluid volume was positively correlated with the postinjury period., Clinical Relevance: Our current human study and previous animal studies suggest the possibility that mesenchymal stem cells in synovial fluid increase after meniscus injury contributing to spontaneous meniscus healing.

Background: Fresh osteochondral allograft transplantation is an increasingly common treatment option for chondral and osteochondral lesions in the knee, but the long-term outcome is unknown., Questions/purposes: We determined (1) pain and function, (2) frequency and types of reoperations, (3) survivorship at a median of 13.5 years, and (4) predictors of osteochondral allograft failure in the distal femur., Methods: We evaluated 122 patients (129 knees) who underwent osteochondral allograft transplantation of the femoral condyle. Mean age was 33 years and 53% were male. Clinical evaluation included the modified Merle d'Aubigné-Postel (18-point), IKDC, and Knee Society function (KS-F) scores. We defined graft failure as revision osteochondral allografting or conversion to arthroplasty. We determined whether patient characteristics or attributes of the graft influenced failure. Minimum followup was 2.4 years (median, 13.5 years); 91% had more than 10 years of followup., Results: Mean modified Merle d'Aubigné-Postel score improved from 12.1 to 16, mean IKDC pain score from 7.0 to 3.8, mean IKDC function score from 3.4 to 7.2, and mean KS-F score from 65.6 to 82.5. Sixty-one knees (47%) underwent reoperations. Thirty-one knees (24%) failed at a mean of 7.2 years. Survivorship was 82% at 10 years, 74% at 15 years, and 66% at 20 years. Age of more than 30 years at time of surgery and having two or more previous surgeries for the operated knee were associated with allograft failure., Conclusions: Followup of femoral condyle osteochondral allografting demonstrated durable improvement in pain and function, with graft survivorship of 82% at 10 years.

Background: Clinical cartilage restoration is evolving, with established and emerging technologies. Randomized, prospective studies with adequate power comparing the myriad of surgical techniques used to treat chondral injuries are still lacking and it remains a challenge for the surgeon treating patients to make evidence-based decisions., Questions/purposes: We reviewed the history of the major cartilage repair/restorative procedures, indications for currently available repair/restorative procedures, and postoperative management., Methods: We performed searches using MEDLINE and cartilage-specific key words to identify all English-language literature. Articles were selected based on their contributions to our current understanding of the basic science and clinical treatment of articular cartilage lesions or historical importance. We then selected 77 articles, two of which are articles of historical importance., Results: Current cartilage restorative techniques include débridement, microfracture, osteochondral fragment repair, osteochondral allograft, osteochondral autograft, and autologous chondrocyte transplantation. Pending techniques include two-staged cell-based therapies integrated into a variety of scaffolds, single-stage cell-based therapy, and augmentation of marrow stimulation, each with suggested indications including lesion size, location, and activity demands of the patient. The literature demonstrates variable improvements in pain and function contingent upon multiple variables including indications and application., Conclusions: For the patient with symptomatic chondral injury, numerous techniques are available to the surgeon to relieve pain and improve function. Until rigorous clinical trials (prospective, adequately powered, randomized control) are available, treatment decisions should be guided by expert extrapolation of the available literature based in historically sound principles.

The importance of the menisci to the well-being of the normal knee is well-documented. However, there is no ideal repair or reconstructive approach for damaged menisci. Gene therapy provides one promising alternative strategy, especially when combined with injectable tissue engineering to achieve minimally invasive clinical application. We asked whether the introduction of human insulin-like growth factor 1 (hIGF-1) gene could improve the repair of full-thickness meniscal defects. We created full-thickness meniscal defects in the "white area" of the anterior horn in 48 goats. Bone marrow stromal cells with the transfection of hIGF-1 gene and injectable calcium alginate gel were mixed together to repair the defects; three control groups included cells without transfection, gel without cells, and defects left empty. After 4, 8, and 16 weeks, the animals were euthanized and the excised defects were examined by macroscopic assessment, histological analysis, electron microscopy, proteoglycan determination, and MRI. Sixteen weeks after surgery the repaired meniscal defects were filled with white tissue similar to that in normal meniscal fibrocartilage. The repair tissue was composed of cells embedded within matrix that filled the spaces of the fibers. The proteoglycan content in the gene-enhanced tissue engineering group was higher than those in the control groups, and less than that in the normal meniscus. The results suggest full-thickness meniscal defects in regions without blood supply can be reconstructed with hIGF-1-enhanced injectable tissue engineering.

Unlabelled: The posterior inclination of the tibial plateau, which is referred to as posterior tibial slope, is determined routinely on lateral radiographs. However, radiographically, it is not always possible to reliably recognize the lateral plateau, making a separate assessment of the medial and lateral plateaus difficult. We propose a technique to measure the plateaus separately by defining a tibial longitudinal axis on a conventional MRI. The medial plateau posterior tibial slope obtained from radiographs was compared with MR images in 100 consecutive patients with knee pain when ligament or meniscal injury was assumed. The posterior tibial slope on MRI correlated with those on radiographs. The mean posterior tibial slope was 3.4 degrees smaller on MRI compared with radiographs (4.8 degrees +/- 2.4 degrees versus 8.2 degrees +/- 2.8 degrees , respectively). The reproducibility was slightly better on radiographs than MRI (+/- 0.9 degrees versus +/- 1.4 degrees ). Twenty-one of the 100 cases had more than a 5 degrees difference (range, -8.7 degrees to 8.9 degrees ) between the medial and lateral plateaus. The proposed technique allows measurement of the posterior tibial slope of the medial and lateral plateaus on a standard knee MRI. By using this novel measurement technique, a reliable assessment of the medial and lateral tibial plateaus is possible., Level of Evidence: Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

We report the case of a bilateral bipartite ossification center of the proximal tibia in a 15-year-old boy with a history of knee injury. The presence of the duplicated ossific centers was an incidental finding on radiography and computed tomography performed after injury. Arthroscopy showed continuous hyaline cartilage between the two ossific centers confirming the diagnosis of a developmental abnormality; however, the articular surface was depressed in the region overlying the smaller ossific center. We presume the presence of an accessory center in the posteromedial aspect of the tibial plate could be a source of instability for the corresponding capsular and meniscal structures. This is, to our knowledge, the first report of tibial bipartite epiphysis.

Rupture of the quadriceps tendon is an uncommon injury and rapid diagnosis is important because delay in surgical repair generally is believed to adversely affect outcome. One study of 20 patients suggests repair should be done during the first 48 to 72 hours postinjury to achieve a successful outcome and late repair led to unsatisfactory recovery. Cases of delayed tendon repair have been reported, the longest to our knowledge being 11 months before surgical intervention. We present a case of successful outcome of a quadriceps tendon rupture reconstructed at least 8 years after occurrence and a review of the literature of delayed reconstructions. We show that successful restoration of extensor mechanism function can be achieved several years after tendon rupture.

Unlabelled: Preoperatively predicting chondral damage is important. Weightbearing radiographs, including the standing anteroposterior and 45 degrees flexion posteroanterior views traditionally have been used for this purpose. We wanted to determine if one radiograph had superior sensitivity or specificity in detecting arthroscopically confirmed Grade II chondromalacia (mild arthritis). A standard prospective standing radiographic protocol was designed for all patients who presented to a sports medicine center with knee complaints. Patients who had subsequent arthroscopic surgery had their radiographs measured in a blinded manner for articular cartilage intervals in millimeters to detect joint-space narrowing. Intraarticular chondral damage was correlated with the radiographic findings. Three hundred forty-nine of a possible 411 (87%) patients during a 2-year period had both radiographs and subsequent arthroscopic grading of chondromalacia. This has been the largest study that correlated arthroscopic chondromalacia grades with two commonly preferred weightbearing radiograph projections. Despite specificities greater than 90%, the sensitivity was extremely low and neither standing radiograph was superior. Neither radiograph was useful in detecting Grade II chondral damage., Level of Evidence: Diagnostic study, Level I-1 (testing of previously developed diagnostic criteria in series of consecutive patients--with universally applied reference "gold" standard). See the Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: Peterson's pioneering experience with the first clinical application of autologous chondrocyte implantation showed improvement in clinical outcomes, durable as much as 11 years, for a difficult patient population. An assessment of the general applicability of this technology in the United States requires long-term, multicenter followup. The purpose of this multicenter cohort study was to assess the clinical outcomes of patients treated with autologous chondrocyte implantation for lesions of the distal femur. Modified 10-point scales of the Cincinnati knee rating system were used to measure outcomes assessments at baseline and at 5 years. Eighty-seven percent (87 of 100) of patients completed 5-year followup assessments. Patients were an average 37 years of age, had a mean total defect size of 4.9 cm2, and had low baseline overall condition scores. At least one prior cartilage repair procedure had failed in 70% of the patients. At followup, 87 patients reported a mean improvement of 2.6 points in the overall condition score, including 62 with improved conditions, six with no change in condition, and 19 with worsened conditions. Of the 62 patients who improved, the mean overall condition score improved 4.1 points at followup. Patients treated with autologous chondrocyte implantation for large cartilage defects in the distal femur reported improvement in outcome scores at 5 years followup., Level of Evidence: Therapeutic study, Level II-1 (prospective cohort study). See the Guidelines for Authors for a complete description of levels of evidence.

Chondrocytes undergo apoptosis in response to mechanical injury in vitro. The current clinical study correlates arthroscopic and magnetic resonance imaging results with biopsy specimens of cartilage from patients with knee injury. Twenty patients were evaluated at a mean 2.7 months after acute knee injury. The mean age of the patients was 32 years and the mean weight was 83 kg. Cartilage lesions were graded separately on magnetic resonance images and arthroscopy in a blinded manner. During arthroscopy, a 1.8 mm diameter biopsy specimen was obtained from the edge of cartilage lesion. The biopsy specimen underwent histologic examination by safranin O staining and detection of chondrocyte apoptosis by the presence of deoxyribonucleic acid fragmentation. There was a positive correlation in 50% (10 of 20) when the presence or absence of cartilage lesions by magnetic resonance imaging was correlated with arthroscopy. All cases of partial thickness or full-thickness cartilage loss that were seen by arthroscopy also were detected by magnetic resonance images. Apoptotic cells were significantly more numerous in biopsy specimens from lesions compared with control biopsy specimens. The findings of reduced cell viability attributable to apoptosis may have profound implications for cartilage repair. This opens potential therapeutic avenues for the treatment of posttraumatic cartilage lesions through apoptosis prevention.

Reconstruction of the anterior cruciate ligament is a delicate task for which many different techniques have been proposed. A system consisting of a computer and a three-dimensional optical sensor is proposed to help the surgeon control the placement of a graft. This system can be used to minimize anisometry of the graft and avoid notch impingement. The same system, which had been validated by previous testing on 20 fresh human anatomic specimen knees, was tested on 23 patients who had an anterior cruciate ligament injury. Tunnel placement was performed using the standard technique of Morgan et al and was measured with the computer based system. It was found that all cases had different configurations of tibial and femoral placement. The computer based anisometry measurements ranged from 1.9 mm to 8.8 mm in the anterior part of the graft, and from 1 mm to 13 mm in the centers of the tunnels. Using the computer retrospectively, it was possible to find configurations of the graft in all cases that avoid notch impingement, with anisometry values ranging from 1.3 mm to 3.7 mm. This study shows that a computer based system can be a useful tool for routine anterior cruciate ligament reconstruction and can be useful for research purposes.

Magnetic resonance imaging has been said to be highly reliable for diagnosis of acute posterior cruciate ligament insufficiency. In the present study, 13 patients whose posterior cruciate ligament insufficiency had been documented by magnetic resonance imaging within 10 weeks of the acute injury were recalled for a followup examination and magnetic resonance imaging. The followup interval ranged from 5 months to 4 years. In only 23% of the cases did the posterior cruciate ligament still appear discontinuous on followup magnetic resonance imaging. In the remaining 77%, the posterior cruciate ligament was continuous from tibia to femur, although it appeared abnormally arcuate or hyperbuckled. Conventional interpretation of these magnetic resonance images would suggest that the posterior cruciate ligament had healed. Nevertheless, by clinical examination results, these same patients all were judged to have posterior cruciate ligament insufficiency. Thus, it was concluded that although magnetic resonance imaging may be reliable for evaluation of acute posterior cruciate ligament injury, magnetic resonance imaging findings should not be used to infer functional status in chronic cases.

The effect of a single local injection of long acting corticosteroid on the healing of acute rat medial collateral ligament injuries was studied. The medial collateral ligaments of 81 adult female rats were exposed surgically. In 32 rats, the ligament was transected sharply, the overlying muscle was closed, and a human equivalent dose of dexamethasone was injected under the muscle layer, bathing the injured ligament. The identical operation with no corticosteroid injection was done in 32 additional rats: in the remaining 17 animals, the incision was closed without ligament transection or injection. The rats were divided into 3 groups of 25. Each group consisted of 10 rats that were injected, 10 that were not injected, and 5 that underwent sham operations. One group was euthanized 6 days after surgery, 1 group after 10 days, and 1 group after 20 days. Histologic evaluation and biomechanical testing were performed for each subgroup. A cellular pathologist examined a smaller group of 6 rats (2 from each group) for histologic changes 40 days after surgery. No histologic differences were noted between the injected and noninjected ligaments 6, 10, or 20 days after injury. At 40 days, the injected specimens showed a slightly more mature crimp pattern than the noninjected specimens. Mechanical testing demonstrated no significant difference in ultimate load or ultimate stress between the injected and noninjected groups. There were no detrimental effects of a single dose administration of dexamethasone on the histologic appearance or biomechanical strength of healing rat medial collateral ligaments.

Analytic stereophotogrammetry and an interactive computer graphics program were used to obtain first order assessments of joint contact patterns in patellofemoral and glenohumeral joints, simulating normal and abnormal articulations. Precise (90 microns accuracy) computer graphic representations of the humeral head, glenoid, patella, and femoral articular surfaces were obtained from cadaver knees and shoulders. These surface representations were then manipulated into an articulated position, and joint contact areas computed by a proximity criterion. Pathologic states were then simulated, and contact recomputed. Simulated glenohumeral subluxations dramatically reduced contact area, and focused it eccentrically on the glenoid rim. Simulated size mismatch of humeral heads to glenoids reduced contact area, producing a pattern of peripheral contact on the glenoid if the humeral head had a larger radius of curvature, and central contact on the glenoid if the humeral head had a smaller radius of curvature. At 30 degrees knee flexion, the patellofemoral joint demonstrated a broad distribution of contact along the distal aspect of the patella and proximal aspect of the trochlea. Simulated lateral tilt (5 degrees) and translation (5 mm) of the patella resulted in shift of the predominant contact area laterally, along with a drastic decrease in the contact area. These results have implications for prosthetic sizing and biomechanical modeling of the glenohumeral and patellofemoral joints, and in selecting models for more rigorous empiric studies of joint contact. Furthermore, this technique allows a first order assessment of the effects of specific surgical reconstructions on articular mechanics.

The pathologic description of the menisci is facilitated by grouping the various disorders into etiologic groups. These include congenital anomalies, traumatic conditions, inflammatory disorders, metabolic disorders, degenerative conditions, and neoplasms. In clinical practice, traumatic conditions, as exemplified by meniscal tears of the vertical-longitudinal or vertical-transverse type, are the most important pathologic disorders. Healing of meniscal tears occurs only when the tear involves the peripheral vascularized attachment of either the lateral or medial meniscus. Intensive clinical and animal experimentation suggests that serum-derived growth factors are necessary for meniscal healing. Chondrocalcinosis is extremely frequent in the menisci of older individuals and may or may not be associated with degenerative changes of the menisci, including fibrillation, loss of protein polysaccharide ground substance, and chondrocytic proliferation. The role of degenerative changes of the menisci, including tears of the horizontal type, in the development of osteoarthritis (OA) of the knee is a subject of intense interest, as is the relationship between chondrocalcinosis and OA. Neoplastic involvement of the menisci is essentially limited to invasion by tumors starting in or, more commonly, adjacent to the knee joints.

Ninety-three knees with patellar instability were repaired after conservative treatment failed. In 34 there was evidence of tibiofemoral incongruity consisting of an articular depression of the medial femoral condyle by the meniscus. Secondary articular invasion by synovium occurred in 20 knees. Certain clinical phenomena indicate the presence of this impingement lesion: distinct tenderness over the joint line anterior to the medial collateral ligament, pseudo-locking, and increased pain when walking with the tibia rotated externally. These findings are in addition to the usual parapatellar tenderness, apprehension sign, and crepitus encountered in patellar instability. Excessive external tibial rotation is the probable cause of the impingement rather than genu valgum or dysplasia of the vastus medialis. Hypertension may be a factor. The lesion may play a role in the genesis of osteoarthritis subsequent to patellar instability. Transfer of the tibial tubercle medially may be expected to aggravate tibiofemoral incongruity by increasing tibial external rotation. Other procedures are preferred for patellar stabilization.

Fractures of the proximal tibia involving the articular surfaces vary greatly in type, severity, and prognosis, and a considerable percentage have significant associated ligamentous injuries. This report classifies and analyzes 132 particular fractures separated from over 1,000 patients with fractures of the proximal tibia. The remaining cases were considered to have tibial plateau fractures. Eighty-six fractures required operative treatment, and it was possible to divide them into five distinct types. The characteristic of these five types is marked joint instability with a high incidence of serious soft-tissue and/or neurovascular injury. Knee dislocation is a discrete entity. Plateau fracture is a discrete entity that requires definition (and which in large measure has little or no implication of significant soft-tissue injury). Fracture--dislocation of the knee is a much more serious injury than plateau fracture. For successful treatment of this injury, a radically different understanding of fractures of the proximal tibial condyles is needed.

The traditional method for testing for anterior stability of the knee has often lead to inaccurate assessment of ligament stability because of the jerky nature of the test and the small amount of force applied. A method of testing the anterior drawer of a knee by flexing the hip and knee to 90 degrees and applying a steady upward force using the body weight as counterpull provides a more reliable test for assessing ligament stability. This method can be used to overcome hamstring spasm and causes less pain in the acutely injured knee.

Cytologic analysis of filtered synovial lavage was compared with the independent arthroscopic findings in 70 patients with knee pain secondary to injury. Correlation existed between the arthroscopic evaluation of the articular surfaces and the presence of cartilaginous fragments and their microscopic features. Study of the filtered lavage was carried out without knowledge of the patient's clinical status or arthroscopic findings. Patients with unblemished articular surfaces and normal menisci demonstrated essentially no fragments in the synovial lavage. Minimal fibrillation of the articular surface with normal menisci was associated with few cartilage fragments per sample. Patients with moderate to severe fibrillation of the articular surface requiring a surface altering procedure, demonstrated significantly more fragments per sample. Chondrocyte nuclei were visible in these fragments, often arranged in multicellular clusters. Isolated lesions of the meniscus were associated with cartilage fragments that did not contain chondrocyte nuclei. Microscopic analysis of synovial lavage may serve as a useful diagnostic adjunct in the evaluation of the painful knee and the study of the pathogenic role of cartilage fragments is osteoarthrosis.

The similarity of the histopathologic changes in posttraumatic synovitis and osteoarthritis suggests that similar etiologic agents, possibly macro- and microtraumata, were pathogenetic factors in common.

In the management of a number of acute and chronic knee ligament injuries it was noted that the patterns of displacement could be explained on a translational basis in one of two planes. The displacement could be predicted by the anatomical structures that were torn. Rotation, while present in some cases, was not the major pattern of instability. It is therefore logical to classify knee ligament injuries on an anatomical basis. The injury or combination of injuries produces a predictable pattern of instability. Anatomical classification based on patterns of instability is less confusing than some methods of classification currently in use and may aid in clinical management.

This is a demonstration of local traumatization of articular cartilage inducing mitoses in parts of a joint other than the site of inquiry. Parts of one of the patellar cartilages of the full-grown rabbit were scored while the other knee was subjected only to arthrotomy. Radioactive thymidine and autoradiographic technique demonstrated that labeled chondrocytes appeared not only around the score in the patella but also scattered in the tibia and femoral condyles. Whether the mechanism of regional mitotic stimulation is a reduction of the concentration of the normal cell specific inhibitors of mitosis, or so-called chalones is not known and requires further investigation.