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Background: The incidence of subsequent posttraumatic osteoarthritis (OA) diagnosis after surgery and the associated risk factors have been well reported after single-ligament anterior cruciate ligament (ACL) reconstruction; however, to date, the incidence of posttraumatic OA for those who have experienced multiligament knee injury (MLKI) has been reported only in relatively small, single-center studies. Purpose: To compare the incidence of OA diagnoses between patients with ACL injury versus patients with MLKI and to identify risk factors for OA diagnosis after MLKI. Study Design: Cohort study; Level of evidence, 3. Methods: This study used the PearlDiver Mariner database, which contains insurance claims information on >151 million orthopaedic patients. We identified 2 cohorts for this study by using Current Procedural Terminology codes. The cohorts included patients between the ages of 16 and 60 who underwent either isolated ACL reconstruction (n = 114,282) or MLKI reconstruction (n = 3325) between July 1, 2010, and August 30, 2016. MLKI reconstruction was operationally defined as ACL reconstruction plus concurrent surgical treatment of ≥1 additional ligaments. Demographic factors, concomitant meniscal and cartilage procedures, and subsequent reoperation to restore motion were recorded, as was the incidence of knee OA diagnosis within 5 years of the index surgical procedure. OA incidence and demographic and surgical factors were compared (1) between ACL and MLKI groups and (2) between patients with MLKI either with or without OA diagnosis. Results: A significantly greater proportion of patients with MLKI were diagnosed with knee OA within 5 years of surgery (MLKI = 299/3325 [9.0%] vs ACL = 6955/114,282 [6.1%]; P < .0001) (odds ratio [OR], 1.52; 95% CI, 1.35-1.72; P < .001). Factors associated with increased odds of OA diagnosis after MLKI included age ≥30 years (OR, 5.90), reoperation to restore motion (OR, 2.54), obesity (OR, 1.96), mood disorder diagnoses (OR, 1.85), partial meniscectomy (OR, 1.85), and tobacco use (OR, 1.72). Concomitant meniscal repair was protective against OA diagnosis (OR, 0.06). Conclusion: OA incidence was greater after MLKI reconstruction than after isolated ACL reconstruction. Potentially modifiable risk factors for OA after MLKI were identified and include obesity, tobacco use, depression, and the need for motion-restoring surgery.

Background: Anterior cruciate ligament (ACL) tear (ACLT) leads to protracted quadriceps muscle atrophy. Protein turnover largely dictates muscle size and is highly responsive to injury and loading. Regulation of quadriceps molecular protein synthetic machinery after ACLT has largely been unexplored, limiting development of targeted therapies. Purpose: To define the effect of ACLT on (1) the activation of protein synthetic and catabolic signaling within quadriceps biopsy specimens from human participants and (2) the time course of alterations to protein synthesis and its molecular regulation in a mouse ACL injury model. Study Design: Descriptive laboratory study. Methods: Muscle biopsy specimens were obtained from the ACL-injured and noninjured vastus lateralis of young adult humans after an overnight fast (N = 21; mean ± SD, 19 ± 5 years). Mice had their limbs assigned to ACLT or control, and whole quadriceps were collected 6 hours or 1, 3, or 7 days after injury with puromycin injected before tissue collection for assessment of relative protein synthesis. Muscle fiber size and expression and phosphorylation of protein anabolic and catabolic signaling proteins were assessed at the protein and transcript levels (RNA sequencing). Results: Human quadriceps showed reduced phosphorylation of ribosomal protein S6 (–41%) in the ACL-injured limb ( P = .008), in addition to elevated phosphorylation of eukaryotic initiation factor 2α (+98%; P = .006), indicative of depressed protein anabolic signaling in the injured limb. No differences in E3 ubiquitin ligase expression were noted. Protein synthesis was lower at 1 day ( P = .01 vs control limb) and 3 days ( P = .002 vs control limb) after ACLT in mice. Pathway analyses revealed shared molecular alterations between human and mouse quadriceps after ACLT. Conclusion: (1) Global protein synthesis and anabolic signaling deficits occur in the quadriceps in response to ACL injury, without notable changes in measured markers of muscle protein catabolism. (2) Importantly, these deficits occur before the onset of significant atrophy, underscoring the need for early intervention. Clinical Relevance: These findings suggest that blunted protein anabolism as opposed to increased catabolism likely mediates quadriceps atrophy after ACL injury. Thus, future interventions should aim to restore muscle protein anabolism rapidly after ACLT.

Objective and design The purpose of this study was to compare synovial concentrations of pro- and anti-inflammatory cytokines between multiple-ligament knee injured (MLKI) and anterior cruciate ligament (ACL)-injured patients. Subjects 14 patients with MLKI and 10 patients with isolated ACL injury Methods Synovial fluid was aspirated from the operative knee at the time of surgery and the concentrations of pro- and anti-inflammatory markers in the synovial fluid were determined. Structures injured, the time between injury and surgery, and demographic factors were collected. Linear regressions were used to determine the association between injury pattern and synovial inflammatory markers when controlling for age, BMI, and time between injury and surgery. Results When adjusting for group differences in age, BMI and the time between injury and surgery, no group differences were detected (interferon gamma (p = 0.11), interleukin-1beta (IL-1b, p = 0.35), IL-2 (p = 0.28), IL-4 (p = 0.64), IL-6 (p = 0.37), IL-8 (p = 0.54), IL-10 (p = 0.25), IL-12p70 (p = 0.81), IL-13 (p = 0.31), and tumor necrosis factor-alpha (p = 0.90)). Conclusion Synovial fluid inflammatory markers did not differ between MLKI and isolated ACL injuries. MLKIs have a greater prevalence of postoperative arthrofibrosis when compared to isolated ACL injuries; however, this may be due in part to factors other than the inflammatory status of the joint.

Objectives The National Football League (NFL) altered the 2020 season due to the COVID-19 pandemic, which resulted in cancelled preseason games and a dynamic regular season schedule to accommodate for cancelled games. The purpose of this study was to evaluate if the disrupted training and preseason schedule lead to increased injury rates as seen in other professional sports. We hypothesized that the overall injury rate would be higher in the 2020 season compared to the 2018-2019 seasons, and that this increase will affect all body regions equally. Methods : Publicly released NFL weekly injury reports were queried to identify players listed as out or placed on the injured reserve for at least one game in the 2018-2020 seasons. Injuries were categorized into upper extremity, lower extremity, spine/core, head, illness, not injury related and undisclosed injuries. Incidence per 1000 athlete exposures was calculated for the prior two seasons (2018-2019) and for the 2020 season separately. Percentage of injuries occurring in each position were calculated separately for the pre-COVID-19 (2018 and 2019) and post-COVID-19 (2020) cohorts. Incidence rate ratios (IRR) and confidence intervals were used to compare injury rates in 2018-2019 versus 2020. The z-test for proportions was used to determine significant differences between injury incidences. Results : The overall incidence rate per 1000 athlete exposures in 2020 was not significantly different compared to pre-COVID-19 seasons (21.6 versus 23.1, IRR 0.94, 95% CI: 0.9-1.0 p>0.999). The proportion of injuries by position did not change before and after COVID-19 either (p>0.999). Out listings due to illness were significantly increased during the 2020 season (0.8 versus 0.3, IRR 2.8, 95% CI: 1.4-5.2, p=0.004). Conclusion The incidence of NFL injuries did not significantly change in 2020. The distribution of injuries did not change with respect to position.

Meniscal injuries in elite athletes are a common cause of missed game time and even have the potential to be career shortening. In this patient group, care must be paid not only to the pathology, but also to a player’s contract status, time in the season, specific demands of his/her sport and position on the field, and future consequences. Successful treatment requires the clinician to understand the player’s goals and needs, communicate effectively between all stakeholders, and a have knowledge of the challenges posed by the different types of meniscal tear seen in this population. Paramount is the distinction between injuries to the medial and lateral meniscus. Deficiency of the lateral meniscus, as a result of a tear or a meniscectomy, leads to frequent early problems and inexorably to chondral degeneration thereby affecting an athlete’s ability to perform. Therefore, it is strongly recommended to repair the majority of lateral meniscal tears. Medial meniscal tears pose a more challenging treatment dilemma, as the success of partial meniscectomy in achieving reproducible, early return to play must be balanced against the long-term degenerative consequences. Many meniscal tears are correctly treated non-operatively. Level of evidence V.

The objective of the study was to determine if psychological readiness for sport and knee self-efficacy assessed early (3 months) after anterior cruciate ligament reconstruction (ACLR) are predictive of self-reported functional outcomes, quadriceps strength, and knee mechanics while running at the time of return to sport training (6 months). Thirty athletes with unilateral ACLR completed the ACL Return to Sport after Injury (ACL-RSI) and Knee Self-Efficacy Scale (K-SES) 3 months after ACLR and completed self-reported functional outcomes, isometric quadriceps strength testing, and three-dimensional running gait analysis 6 months after ACLR. The 3-month ACL-RSI significantly correlated with the 6-month International Knee Documentation Committee (IKDC; r = 0.565, p = 0.001), Knee Injury and Osteoarthritis Outcome Score (KOOS) sport/recreational activities (KOOSSport ; r = 0.548, p = 0.002) and quality of life (KOOSQoL ; r = 0.431, p = 0.017), and quadriceps strength (r = 0.528, p = 0.003). The 3-month K-SES significantly correlated with the 6-month IKDC (r = 0.528, p = 0.003), KOOSSport (r = 0.430, p = 0.018), KOOSQoL (r = 0.411, p = 0.024), quadriceps strength (r = 0.465, p = 0.010), and knee flexion excursion (r = 0.472, p = 0.008). With multivariate modeling, both the ACL-RSI and K-SES were predictive of the IKDC (R2 = 0.411; p = 0.001). Only the ACL-RSI was predictive of the KOOSSport (R2 = 0.300; p = 0.002), KOOSQoL (R2 = 0.186; p = 0.017), and quadriceps strength (R2 = 0.279; p = 0.003), whereas only the K-SES was predictive of knee flexion excursion (R2 = 0.173; p = 0.022). Athletes with greater psychological readiness for sport and knee self-efficacy at 3 months demonstrated higher scores on self-reported functional outcomes, greater quadriceps strength, and greater knee flexion excursion at 6 months after ACLR. This study indicates that psychosocial measures may be important to include into early post-surgical evaluations to help guide and facilitate interventions to restore subjective and objective knee function.

Background: In the skeletally mature anterior cruciate ligament (ACL) reconstruction population, patients aged Purpose: To examine the incidence of ipsilateral graft failure and contralateral ACL injury in the skeletally immature patient population. Study Design: Systematic review and meta-analysis. Methods: Using the PRISMA (Preferred Reporting Items for Systematic Meta-Analyses) guidelines, we reviewed all literature that involved ACL reconstruction performed on skeletally immature patients between May 1976 and May 2019. Patient demographics, surgical technique, and the prevalence of ipsilateral graft failure or subsequent contralateral ACL injury were recorded. Ipsilateral, contralateral, and secondary ACL injuries were then compared between sexes via chi-square tests. Results: A total of 24 articles (1254 children; 1258 knees) met inclusion criteria for analysis. Ipsilateral graft failures occurred in 105 of 1258 patients (8.3%), and there were no statistically significant sex differences in the prevalence of graft failures (female, 9.7%; male patients, 7.1%; P = .14). The prevalence of contralateral ACL injury was significantly greater in female (29/129; 22.5%) than male (18/206; 8.7%; P = .0004) patients in the 9 studies that reported contralateral injury. Skeletally immature female patients were at significantly increased risk of contralateral ACL injury (odds ratio = 3.0; P = .0006) when compared with their male counterparts. Conclusion: In the literature to date, 1 in 3 female skeletally immature patients experienced an ipsilateral graft failure or contralateral ACL injury. Regardless of sex, the 24% prevalence of secondary injury after pediatric ACL reconstruction is almost identical to previously published secondary injury rates in skeletally mature patients

Anterior cruciate ligament (ACL) injury leads to a sustained increase in synovial fluid concentrations of inflammatory cytokines and biomarkers of cartilage breakdown. While this has been documented post-injury, it remains unclear whether ACL reconstruction surgery contributes to the inflammatory process and/or cartilage breakdown. This study is a secondary analysis of 14 patients (nine males/five females, mean age = 9, mean BMI = 28) enrolled in an IRB-approved randomized clinical trial. Arthrocentesis was performed at initial presentation (mean = 6 days post-injury), immediately prior to surgery (mean = 23 days post-injury), 1-week post-surgery, and 1-month post-surgery. Enzyme-linked immunosorbant assay kits were used to determine concentrations of carboxy-terminal telopeptides of type II collagen (CTXII), interleukin-6 (IL-6), and IL-1β in the synovial fluid. The log-transformed IL-1β was not normally distributed; therefore, changes between time points were evaluated using a non-parametric Kruskal-Wallis one-way ANOVA. IL-1β concentrations significantly increased from the day of surgery to the first postoperative time point (P ≤ .001) and significantly decreased at the 4-week postoperative visit (P = .03). IL-1β concentrations at the 4-week postoperative visit remained significantly greater than both preoperative time points (P .05). IL-6 concentrations at 1-week post-surgery were significantly higher than at initial presentation (P = .013), the day of surgery (P .001), and 4 weeks after surgery (P = .002). CTX-II concentrations did not differ between the first three-time points (P .99) but significantly increased at 4 weeks post-surgery (P .01). ACL reconstruction appears to reinitiate an inflammatory response followed by an increase in markers for cartilage degradation. ACL reconstruction appears to initiate a second "inflammatory hit" resulting in increased chondral breakdown suggesting that post-operative chondroprotection may be needed.

OBJECTIVE To determine the relationship between patient-reported outcomes (PROs) to the single-leg step-down test (SLSD) and the Y-balance anterior reach (YB-A) 6 months after primary anterior cruciate ligament reconstruction (ACLR). DESIGN Cross-sectional. SETTING Laboratory. PARTICIPANTS Sixty-six patients 6 months after ACLR participated. INTERVENTIONS Patients performed the SLSD, YB-A, and completed PROs after ACLR. MAIN OUTCOME MEASURES Patients completed the International Knee Documentation Committee Score (IKDC), the Lysholm Activity Scale, the Tampa Scale of Kinesiophobia (TSK-11), and the Knee Injury and Osteoarthritis Outcome Score (KOOS)-Symptom, -Sport, and -Quality of Life (QOL) subscales. The SLSD requires subjects to complete as many single-leg step-downs as possible in 60 seconds, and the YB-A involves reaching anteriorly on a single limb. Pearson product moment correlations were used to assess relationships between the YB-A and SLSD performance to each PRO. RESULTS Single-leg step-down test symmetry was significantly correlated with the TSK-11 (r = -0.70), KOOS-Sport (r = 0.40), -Symptom (r = 0.46), and -QOL (r = 0.42). The YB-A symmetry was significantly correlated with the KOOS-Symptom (r = 0.30) and KOOS-Sport (r = 0.30). CONCLUSIONS Single-leg step-down test performance demonstrated stronger relationships to patient-reported knee function than the YB-A. Furthermore, the SLSD symmetry was strongly correlated with fear of movement. The SLSD provides a robust method for clinicians to assess dynamic knee function and may aid in identifying patients who could benefit from intervention to reduce fear of movement or reinjury.

Background: Knee joint power is significantly impaired during the propulsive phase of jumping after anterior cruciate ligament reconstruction (ACLR); however, it is currently unknown how quadriceps strength influences knee joint power. Purpose: To (1) evaluate the relationship between quadriceps strength, joint power, and the percentage contribution of the hip, knee, and ankle joints to total limb power during the propulsive phase of jumping and (2) establish a quadriceps strength cutoff value for maximizing the likelihood of having knee joint power characteristics similar to healthy participants. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 75 participants were included in this study—40 patients who underwent ACLR 6 months before (18 females; mean age, 19.3 ± 5.7 years) and 35 healthy controls (HC) (20 females; mean age, 21.5 ± 4.5 years). Participants performed a drop vertical jump and underwent isometric quadriceps strength testing. The peak joint power was calculated as the product of the internal joint moment and joint angular velocity. Pearson product-moment correlations were used to assess the relationship between quadriceps strength and knee joint power. Paired samples t tests were used to quantify differences between limbs. Receiver operating characteristic (ROC) curve analysis was used to determine a quadriceps strength cutoff. Results: The involved limbs of the ACLR cohort (INV) had significantly lower peak knee joint power and percentage contribution from the knee joint during jumping compared with the uninvolved limbs (NON) and limbs of the controls (INV, 2.5 ± 1.2 W/kg; NON, 4.4 ± 1.5 W/kg; HC, 4.3 ± 1.7 W/kg [ P < .0001]). Quadriceps strength was associated with knee joint power in involved limbs and limbs of controls (INV, r = 0.50; HC, r = 0.60). A quadriceps strength cutoff value of 2.07 N·m/kg had an area under the ROC curve of 0.842, indicating good predictive accuracy. Conclusion: Athletes at 6 months after ACLR demonstrated knee-avoidant jumping mechanics and had significant reductions in knee joint power on the involved limb. A quadriceps strength cutoff value of 2.07 N·m/kg can help predict which athletes will display knee joint power characteristics similar to those of healthy controls.

PURPOSE Elevated synovial fluid (SF) concentrations of proinflammatory cytokines, degradative enzymes, and cartilage breakdown markers at the time of anterior cruciate ligament (ACL) reconstruction are associated with worse postoperative patient-reported outcomes and cartilage quality. However, it remains unclear if this is due to a more robust or dysregulated inflammatory response or is a function of a more severe injury. The objective of this study was to evaluate the association of the molecular composition of the SF, patient demographics, and injury characteristics to cartilage degradation after acute ACL injury. METHODS We performed a cluster analysis of SF concentrations of proinflammatory and anti-inflammatory cytokines, and biomarkers of cartilage degradation, bony remodeling, and hemarthrosis. We evaluated the association of biomarker clusters with patient demographics, days between injury, Visual Analogue Scale pain, SF aspirate volumes, and bone bruise volumes measured on magnetic resonance imaging. RESULTS Two clusters were identified from the 35 patients included in this analysis, dysregulated inflammation and low inflammation. The dysregulated inflammation cluster consisted of 10 patients and demonstrated significantly greater concentrations of biomarkers of cartilage degradation (P < 0.05) as well as a lower ratio of anti-inflammatory to proinflammatory cytokines (P = 0.053) when compared with the low inflammation cluster. Patient demographics, bone bruise volumes, SF aspirate volumes, pain, and concomitant injuries did not differ between clusters. CONCLUSIONS A subset of patients exhibited dysregulation of the inflammatory response after acute ACL injury which may increase the risk of posttraumatic osteoarthritis. This response does not appear to be a function of injury severity.

Background: Anterior cruciate ligament (ACL) tears result in significant quadriceps muscle atrophy that is resistant to recovery despite extensive rehabilitation. Recent work suggests an elevated fibrotic burden in the quadriceps muscle after the injury, which may limit recovery. Elucidating the mechanisms and cell types involved in the progression of fibrosis is critical for developing new treatment strategies. Purpose: To identify factors contributing to the elevated fibrotic burden found after the injury. Study Design: Descriptive laboratory study. Methods: After an ACL injury, muscle biopsy specimens were obtained from the injured and noninjured vastus lateralis of young adults (n = 14, mean ± SD: 23 ± 4 years). The expression of myostatin, transforming growth factor β, and other regulatory factors was measured, and immunohistochemical analyses were performed to assess turnover of extracellular matrix components. Results: Injured limb skeletal muscle demonstrated elevated myostatin gene ( P < .005) and protein ( P < .0005) expression, which correlated ( R2 = 0.38, P < .05) with fibroblast cell abundance. Immunohistochemical analysis showed that human fibroblasts express the activin type IIB receptor and that isolated primary human muscle-derived fibroblasts increased proliferation after myostatin treatment in vitro ( P < .05). Collagen 1 and fibronectin, primary components of the muscle extracellular matrix, were significantly higher in the injured limb ( P < .05). The abundance of procollagen 1–expressing cells as well as a novel index of collagen remodeling was also elevated in the injured limb ( P < .05). Conclusion: These findings support a role for myostatin in promoting fibrogenic alterations within skeletal muscle after an ACL injury. Clinical Relevance: The current work shows that the cause of muscle quality decline after ACL injury likely involves elevated myostatin expression, and future studies should explore therapeutic inhibition of myostatin to facilitate improvements in muscle recovery and return to sport.

Context: There is a lack of consensus regarding test batteries for return to sport (RTS) after anterior cruciate ligament reconstruction (ACLR). Objective: To report the RTS test batteries for individuals after ACLR and to examine alignment with the American Academy of Orthopaedic Surgeons (AAOS) Appropriate Use Criteria (AUC). Finally, to examine how published RTS batteries prior to the AAOS AUC (2010-2015) compared with those after publication of the AUC (2016-2020). Data Source: A systematic search of PubMed (2010-2020). Study Selection: Studies were included if they were published from 2010 to 2020, patients underwent primary ACLR and were tested between 6 months and 2 years postoperatively and included a minimum of 2 assessments. Studies were excluded if patients were tested outside the designated time; had undergone a revision, contralateral, or multiligament injury; included healthy participants; were level 5 evidence or the study was a systematic review. A total of 1012 articles were reviewed and 63 met the criteria. Study Design: Systematic review. Level of Evidence: Level 4. Data Extraction: Information regarding the RTS batteries and patient demographics were extracted from the included articles. Results: A total of 63 studies met the inclusion and exclusion criteria (22 from 2010-2015 and 41 from 2016-2020). The most common RTS batteries included the hop test, quadriceps strength test, and patient-reported outcome measures. No study met all 7 AUC; the most common criteria met were functional skills (98.4%), followed by confidence (22.2%), then range of motion and knee stability (20.6%). Conclusion: The test batteries in the current literature show high variability and a lack of essential components necessary for RTS. No study met the AUC guidelines, suggesting a disconnect between recommended guidelines and clinical practice. Test battery research has expanded over the past decade; however, standardized, clinically applicable batteries that encompass all criteria are needed.

Knee injuries can be some of the most devastating in all of sports. A quick and accurate diagnosis is key to the in-season management of the athlete. An accurate diagnosis will allow the physician and athlete to not only come to an understanding of how to expedite return to play, but to understand the risks of operative versus nonoperative management and how the treatment choices will affect the season as well as the athlete’s future. The mission of the team physician is to educate the athlete so that an informed decision can be made regarding the injury. While some knee injuries are relatively straightforward in their treatment algorithm, some can be more complex and require a thorough understanding of the anatomy, the mechanism of injury, the physical examination, and the treatment options. This chapter is designed to help concisely and systematically review common football injuries to the knee sustained in active participation.

Background:Many patients live with long-term deficits in knee function after an anterior cruciate ligament reconstruction (ACLR). However, research is inconclusive as to which physical performance measure is most strongly related to long-term patient-reported outcomes after ACLR.Hypothesis:Quadriceps strength would be most strongly associated with patient-reported long-term outcomes after ACLR.Study Design:Cross-sectional study.Level of Evidence:Level 3.Methods:A total of 40 patients (29 female) consented and participated an average of 10.9 years post-ACLR (range, 5-20 years). Patients completed the Lower Extremity Functional Scale (LEFS), the International Knee Documentation Committee (IKDC) Scale, Knee injury and Osteoarthritis Outcome Score Quality of Life (KOOS QoL) and Sport (KOOS Sport) subscales, and the Tampa Scale of Kinesiophobia (TSK-17). Each patient subsequently performed maximal isometric quadriceps contraction, a 60-second single-leg step-down test, and the single-leg single hop and triple hop for distance tests. Multivariate linear and logistic regression models determined how performance testing was associated with each patient-reported outcome when controlling for time since surgery, age, and TSK-17.Results:When controlling for time since surgery, age at the time of consent, and TSK-17 score, maximal isometric quadriceps strength normalized to body weight was the sole physical performance measure associated with IKDC ( P < 0.001), KOOS Sport ( P = 0.006), KOOS QoL ( P = 0.001), and LEFS scores ( P < 0.001). Single-leg step-down, single hop, and triple hop did not enter any of the linear regression models ( P > 0.20). Additionally, TSK-17 was associated with all patient-reported outcomes ( P ≤ 0.01) while time since surgery was not associated with any outcomes ( P > 0.05).Conclusion:Isometric quadriceps strength and kinesiophobia are significantly associated with long-term patient-reported outcomes after ACLR.Clinical Relevance:These results suggest that training to improve quadriceps strength and addressing kinesiophobia in the late stages of recovery from ACLR may improve long-term self-reported function.

Background. The majority of patients develop posttraumatic osteoarthritis within 15 years of anterior cruciate ligament (ACL) injury. Inflammatory and chondrodegenerative biomarkers have been associated with both pain and the progression of osteoarthritis; however, it remains unclear if preoperative biomarkers differ for patients with inferior postoperative outcomes. Hypothesis/Purpose. The purpose of this pilot study was to compare biomarkers collected on the day of ACL reconstruction between patients with “good” or “poor” 2-year postoperative outcomes. We hypothesized that inflammatory cytokines and chondrodegenerative biomarker concentrations would be significantly greater in patients with poorer outcomes. Study Design. Prospective cohort design. Methods. 22 patients (9 females, 13 males; age = 19.5±4.1 years; BMI = 24.1±3.6 kg/m2) previously enrolled in a randomized trial evaluating early anti-inflammatory treatment after ACL injury. Biomarkers of chondrodegeneration and inflammation were assessed from synovial fluid (sf) samples collected on the day of ACL reconstruction. Participants completed Knee Injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) questionnaires two years following surgery. Patients were then categorized based on whether their KOOS Quality of Life (QOL) score surpassed the Patient Acceptable Symptom State (PASS) threshold of 62.5 points or the IKDC PASS threshold of 75.9 points. Results. Patients that failed to reach the QOL PASS threshold after surgery (n = 6, 27%) had significantly greater sf interleukin-1 alpha (IL-1α; p = 0.004), IL-1 receptor antagonist (IL-1ra; p = 0.03), and matrix metalloproteinase-9 (MMP-9; p = 0.01) concentrations on the day of surgery. Patients that failed to reach the IKDC PASS threshold (n = 9, 41%) had significantly greater sf IL-1α (p = 0.02). Conclusion. These pilot data suggest that initial biochemical changes after injury may be an indicator of poor outcomes that are not mitigated by surgical stabilization alone. Biological adjuvant treatment in addition to ACL reconstruction may be beneficial; however, these data should be used for hypothesis generation and more definitive randomized clinical trials are necessary.

The rates of arthroscopic meniscus repair continue to increase with excellent reported outcomes. Complications, sometimes catastrophic, following meniscus repair may occur. The rate of postoperative complications may be reduced by adequate diagnosis, appropriate patient selection, meniscus repair selection, surgical techniques, and postoperative management. When complications occur, the provider must identify and take steps to rectify as well as prevent further complications from occurring. The purpose of this article is to detail the common diagnostic, technical, and postoperative pitfalls that may result in poor patient outcomes.

Following anterior cruciate ligament reconstruction (ACLR), patients present with greater trunk ipsilateral lean, which may affect knee kinetics and increase re-injury risk. However, there has been little research into neuromuscular factors controlling the trunk and their relation to the knee between healthy and ACLR subjects. This is critical to establish in order to develop more directed and effective interventions.As compared to healthy control subjects, ACLR subjects will demonstrate increased erector spinae and rectus abdominis co-contraction, greater rectus abdominis force and greater hamstring force that is correlated to increased forward trunk lean.Cross-sectional study, Level of Evidence: 3.Eleven healthy and eleven ACLR subjects were matched for age, mass and height. Subjects were asked to run at a self-selected speed while instrumented gait analysis was performed. An anthropometrically scaled OpenSim model was created for each subject. Trunk and hamstring muscle forces from Static Optimization were analyzed at impact peak. Additionally, directed co-contraction ratios were calculated for the erector spinae and erector spinae/rectus abdominis combinations.ACLR subjects showed more balanced erector spinae co-contraction [p0.01], and greater hamstring force [biceps femoris long head (p=0.02), semimembranosus (0.01), semitendinosus (0.01)]. There was no statistical difference for any other muscle group.Despite release to return to sport, ACLR subjects are continuing to increase the stiffness of their trunk as well increase their hamstring force to potentially reduce anterior tibial translation.Clinicians may anticipate ACLR subjects using their erector spinae and hamstrings to maintain a sense of stability in their trunk and at their knee.

There has been an increasing awareness of the importance of the meniscus in maintaining the health and function of the knee. When injured, magnetic resonance imaging (MRI) has become the gold standard to diagnose meniscal tears. The information obtained from the MRI helps determine the need for surgical intervention. To achieve the best patient outcome a surgeon must be able to diagnose a meniscal injury by MRI as well as identify the injury at time of arthroscopy. This article aims to illustrate meniscal pathology utilizing side by side comparison of MRI identified meniscal injuries to its arthroscopic correlate as well as describe treatment options for the injury.

Quadriceps strength and single-leg hop performance are commonly evaluated prior to return to sport after anterior cruciate ligament reconstruction (ACLR). However, few studies have documented potential hip strength deficits after ACLR, or ascertained the relative contribution of quadriceps and hip strength to hop performance.Patients cleared for return to sports drills after ACLR were compared to a control group. Participants' peak isometric knee extension, hip abduction, hip extension, and hip external rotation (HER) strength were measured. Participants also performed single-leg hops, timed hops, triple hops, and crossover hops. Between-limb comparisons for the ACLR to control limb and the non-operative limb were made using independent two-sample and paired sample t tests. Pearson's correlations and stepwise multiple linear regression were used to determine the relationships and predictive ability of limb strength, graft type, sex, and limb dominance to hop performance.Sixty-five subjects, 20 ACLR [11F, age 22.8 (15-45) years, 8.3 ± 2 months post-op, mass 70.47 ± 12.95 kg, height 1.71 ± 0.08 m, Tegner 5.5 (3-9)] and 45 controls [22F, age 25.8 (15-45) years, mass 74.0 ± 15.2 kg, height 1.74 ± 0.1 m, Tegner 6 (3-7)], were tested. Knee extension (4.4 ± 1.5 vs 5.4 ± 1.8 N/kg, p = 0.02), HER (1.4 ± 0.4 vs 1.7 ± 0.5 N/kg, p = 0.04), single-leg hop (146 ± 37 vs 182 ± 38% limb length, p 0.01), triple hop (417 ± 106 vs 519 ± 102% limb length, p 0.01), timed hop (3.3 ± 2.0 vs 2.3 ± 0.6 s, p 0.01), and crossover hop (364 ± 107 vs 446 ± 123% limb length, p = 0.01) were significantly impaired in the operative versus control subject limbs. Similar deficits existed between the operative and non-operative limbs. Knee extension and HER strength were significantly correlated with each of the hop tests, but only HER significantly predicted hop performance.After ACLR, patients have persistent HER strength, knee extension strength, and hop test deficits in the operative limb compared to the control and non-operative limbs, even after starting sport-specific drills. Importantly, HER strength independently predicted hop performance. Based on these findings, to resolve between-limb deficits in strength and hop performance clinicians should include HER strengthening exercises in post-operative rehabilitation.Prognostic Study, Level II.

As the incidence of anterior cruciate ligament (ACL) reconstruction continues to increase, the rate of revision surgery continues to climb. Revision surgery has inherent challenges that must be addressed in order to achieve successful results. The cause of the primary ACL reconstruction failure should be determined, and careful preoperative planning should be performed to address the cause(s) of failure. Each patient undergoing revision surgery should undergo a thorough history and physical examination, receive full length alignment radiographs, lateral radiographs, 45-degree flexion weight-bearing postero-anterior radiographs, and patellofemoral radiographs. 3-dimensional computed topography (CT) scan should be performed to assess tunnel position and widening. Magnetic resonance imaging (MRI) should be used to assess for intra-articular soft tissue pathology. Meniscal tears, meniscal deficiency, anterolateral capsule injuries, bony morphology, age, activity level, connective tissue diseases, infection, graft choice, and tunnel position can all impact the success of ACL reconstruction surgery. Meniscal lesions should be repaired, and in cases of persistent rotatory instability, extra-articular procedures may be indicated. Furthermore, osteotomies may be needed to correct malalignment or excess posterior tibial slope. Depending on the placement and condition of the original femoral and tibial tunnels, revision surgery may be performed in a single procedure or in a staged manner. In most cases, the surgery can be performed in one procedure. Regardless, the surgeon must communicate with the patient openly regarding the implications of revision ACL surgery and the treatment plan should be developed in a shared fashion between the surgeon and the patient.

Anterior cruciate ligament (ACL) injuries are associated with significant loss of strength in knee extensor muscles that persists despite physical therapy. The underlying mechanisms responsible for this protracted muscle weakness are poorly understood; however, we recently showed significant myofiber atrophy and altered muscle phenotype following ACL injury. We sought to further explore perturbations in skeletal muscle morphology and progenitor cell activity following an ACL injury. Muscle biopsies were obtained from the injured and non-injured vastus lateralis of young adults (n = 10) following ACL injury, and histochemical/immunohistochemical analyses were undertaken to determine collagen content, abundance of connective tissue fibroblasts, fibrogenic/adipogenic progenitor (FAP) cells, satellite cells, in addition to indices of muscle fiber denervation and myonuclear apoptosis. The injured limb showed elevated collagen content (p

Anterior cruciate ligament (ACL) ruptures are some of the most common sports-related injuries. Treatment of these injuries with ACL reconstruction has evolved over the last several decades. Anatomic single-bundle ACL reconstruction offers an accurate and reproducible method to reproduce native knee anatomy, restore knee kinematics, and ultimately restore function and decrease long-term degenerative effects. The importance of adequate arthroscopic visualization and a thorough understanding of the native anatomic ACL landmarks are discussed in this article. Furthermore, surgical technique, pearls, pitfalls, potential complications, rehabilitation, and outcomes are reviewed.

Anterior cruciate ligament reconstruction is associated with quadriceps dysfunction and altered knee mechanics, but the relationship between these outcomes is not clear. Inclusion of metrics such as the stability of torque output could provide additional insights into the relationship between quadriceps dysfunction and knee mechanics. The purposes of this study were to: (1) measure the difference in quadriceps force steadiness between anterior cruciate ligament reconstructed and contralateral limbs; and (2) assess the relationship of quadriceps force steadiness and peak torque with knee flexion excursion during running.Twenty-eight participants (14 female, age 20 (5) years) underwent quadriceps strength testing and gait analysis. Force steadiness was measured with the standard deviation and coefficient of variation of the participants' detrended torque. Knee flexion excursion was calculated during the stance phase of running trials. Differences between limbs for force steadiness and peak torque were assessed with paired sample t-tests, and a Pearson's product-moment correlation coefficient determined the relationship between pairs of variables.Anterior cruciate ligament reconstructed limbs presented with a significant deficit in relative force steadiness compared to the contralateral limb (4.03 (1.04) % and 3.58 (1.41) % (P .05), respectively). In addition, the relationship of quadriceps strength and force steadiness with knee flexion excursion was altered in anterior cruciate ligament reconstructed limbs due to the inability of the quadriceps to sustain a controlled force output.These results suggest that considering both the magnitude and quality of force production can provide important insight into comprehensive quadriceps function.

Failed anterior cruciate ligament reconstruction is a complex problem. However, mastering evaluation and management of the failed graft can assist the surgeon in helping an increasingly active patient population. The key to a successful revision surgery is determining why the index operation failed. A detailed history, physical examination, and evaluation of appropriate radiology will give the surgeon an outstanding opportunity to plan to move forward. Understanding the most common reasons for failure outlined in this chapter will assist the skilled sports medicine surgeon in individualizing patient care.

The goal of anterior cruciate ligament reconstruction (ACLR) is to allow patients to return to their previous level of activity with a low rate of re-injury. To meet this goal, every ACL surgeon should strive to restore the native anatomy and kinematics of the knee. Although surgical techniques for ACLR have evolved, rates of ACL re-injury remain high, especially in young, active patients. While some of these reinjures may be unavoidable, many factors remain under the control of the surgeon. Despite all such factors contributing to a successful outcome, improper or non-anatomic tunnel placement remains the most common reported reason for technical failure. Proper knowledge and recreation of the insertional site anatomy of the ACL, on both the femur and tibia, allows surgeons to restore the patient's native anatomy and function. We present our surgical technique and rationale for placement of our ACL femoral and tibial tunnels which we have found easily reproducible and technically straightforward.

Background:It is increasingly recognized that biochemical abnormalities of the joint precede radiographic abnormalities of posttraumatic osteoarthritis (PTOA) by as much as decades. A growing body of evidence strongly suggests that the progression from anterior cruciate ligament (ACL) injury to PTOA is multifactorial, involving the interplay between biomechanical disturbances and biochemical homeostasis of articular cartilage.Purpose:The purposes of this randomized study using an acute ACL injury model were to (1) evaluate the natural progression of inflammatory and chondrodegenerative biomarkers, (2) evaluate the relationship between subjective reports of pain and inflammatory and chondrodegenerative biomarkers, and (3) determine if postinjury arthrocentesis and corticosteroid injection offer the ability to alter this biochemical cascade.Study Design:Randomized controlled trial; Level of evidence, 2.Methods:A total of 49 patients were randomized to 4 groups: group 1 (corticosteroid at 4 days after ACL injury, placebo injection of saline at 2 weeks), group 2 (placebo at 4 days after ACL injury, corticosteroid at 2 weeks), group 3 (corticosteroid at both time intervals), or a placebo group (saline injections at both time intervals). Patient-reported outcome measures and synovial biomarkers were collected at approximately 4 days, 11 days, and 5 weeks after injury. The change between the time points was assessed for all variables using Wilcoxon tests, and the relationship between changes in outcome scores and biomarkers were assessed by calculating Spearman ρ. Outcomes and biomarkers were also compared between the 4 groups using Kruskal-Wallis tests.Results:No adverse events or infections were observed in any study patients. With the exception of matrix metalloproteinase 1 (MMP-1) and tumor necrosis factor–inducible gene 6 (TSG-6), chondrodegenerative markers worsened over the first 5 weeks while all patient-reported outcomes improved during this time, regardless of treatment group. Patient-reported outcomes did not differ between patients receiving corticosteroid injections and the placebo group. However, increases in C-telopeptide of type II collagen (CTX-II), associated with collagen type II breakdown, were significantly greater in the placebo group (1.32 ± 1.10 ng/mL) than in either of the groups that received the corticosteroid injection within the first several days after injury (group 1: 0.23 ± 0.27 ng/mL [ P = .01]; group 3: 0.19 ± 0.34 ng/mL [ P = .01]).Conclusion:PTOA begins at the time of injury and results early on in dramatic matrix changes in the knee. However, it is encouraging that early intervention with an anti-inflammatory agent was able to affect biomarkers of chondral degeneration. Should early intervention lead to meaningful changes in either the onset or severity of symptomatic PTOA, the current treatment paradigm for patients with ACL injury may have to be restructured to include early aspiration and intra-articular intervention.Trial Registration:ClinicalTrials.gov identifier: NCT01692756.

The rates of arthroscopic meniscus repair continue to increase with excellent reported outcomes. Complications, sometimes catastrophic, following meniscus repair may occur. The rate of postoperative complications may be reduced by adequate diagnosis, appropriate patient selection, meniscus repair selection, surgical techniques, and postoperative management. When complications occur, the provider must identify and take steps to rectify as well as prevent further complications from occurring. The purpose of this article is to detail the common diagnostic, technical, and postoperative pitfalls that may result in poor patient outcomes.

Background: Factors and details regarding return to play in elite, collegiate female soccer athletes after an anterior cruciate ligament (ACL) injury and reconstruction have not been well studied. Purpose: To evaluate return to play among collegiate female soccer players, specifically examining the effect of surgical and individual athlete characteristics on the return-to-play rate. Study Design: Descriptive epidemiology study. Methods: Sports medicine and athletic training staff at institutions from the National Collegiate Athletic Association Southeastern Conference (SEC) were contacted to request participation in the study. All institutions were sent a standardized spreadsheet with response choices and instructions regarding athlete inclusion criteria. Athlete, injury, surgical technique, and return-to-play data were requested for ACL reconstructions performed on female soccer athletes at the participating institutions over the previous 8 years. χ2 analyses were used to compare the return-to-play rate by year in school, scholarship status, position, depth chart status, procedure, graft type, graft fixation, concomitant procedures, and previous ACL injuries. Results: All 14 of the SEC institutions chose to participate and provided data. A total of 80 ACL injuries were reported, with 79 surgical reconstructions and return-to-play data for 78 collegiate soccer athletes. The overall return-to-play rate was 85%. There was a statistical significance in return-to-play rates favoring athletes in earlier years of eligibility versus later years ( P < .001). Athletes in eligibility years 4 and 5 combined had a return-to-play rate of only 40%. Scholarship status likewise showed significance ( P < .001), demonstrating a higher return-to-play rate for scholarship athletes (91%) versus nonscholarship athletes (46%). No significant differences in return-to-play rates were observed based on surgical factors, including concomitant knee procedures, graft type, and graft fixation method. Conclusion: Collegiate female soccer athletes have a high initial return-to-play rate. Undergoing ACL reconstruction earlier in the college career as well as the presence of a scholarship had a positive effect on return to play. Surgical factors including graft type, fixation method, tunnel placement technique, concomitant knee surgeries, and revision status demonstrated no significant effect on the return-to-play rate.

Posterior cruciate ligament (PCL) injuries are extremely rare and most commonly occur in the trauma setting. They can lead to instability, pain, diminished function, and eventual arthrosis. Several techniques of arthroscopic PCL repair for tibial-sided bony avulsions have been described in the literature; however, no single technique has emerged as the gold standard to predictably restore posterior knee stability, PCL function, and knee biomechanics. The authors believe that the best results will come from procedures that re-create the normal human anatomy and knee kinematics. In this article, 3 arthroscopic methods of PCL avulsion repairs performed at 2 academic institutions are analyzed. The techniques described here provide good options for the treatment of these injuries. [ Orthopedics. 2015; 38(9):563–569.]

Background: Recent data from the Danish anterior cruciate ligament (ACL) registry demonstrated increased reoperation rates for hamstring tendon autografts when an anatomic ACL reconstruction is performed. This is consistent with reports of greater time needed for hamstring tendon autografts to mature compared with other autografts. Purpose: To review the literature comparing graft failure rate between patellar and hamstring tendon autografts placed anatomically and to determine if there are differences in return to preinjury activity levels between autografts. Study Design: Systematic review with meta-analysis and meta-regression. Methods: The PubMed, MEDLINE, SPORTDiscus, and CINAHL databases were used to identify studies published from January 1, 2000, through March 7, 2014. To compare postoperative outcomes between patellar tendon and hamstring tendon autografts, summary event rates for graft failure and return to preinjury activity level were calculated. A meta-analysis was performed to calculate a summary odds ratio (OR) for graft failure between autografts using the studies that directly compared the 2 autografts. Meta-regression analyses were performed to assess the influence of postoperative follow-up time on graft failure rate. Results: A total of 28 studies reported graft failures for patellar tendon (6 studies) and hamstring tendon (26 studies) autografts used with anatomic ACL reconstruction; 4 of the 28 were comparison studies. Graft failure rate was not significantly different between patellar tendon (7.0% [95% CI, 4.6%-10.5%]) and hamstring tendon autografts (3.9% [95% CI, 2.7%-5.6%]). The odds of graft failure were slightly higher for hamstring tendon autografts (OR, 1.21 [95% CI, 0.63-2.33]), but this difference was not significant ( P = .57). The rate of patients returning to preinjury activity levels was not significantly different between patellar (n = 1 study; 58.1% [95% CI, 40.4%-73.9%]) and hamstring tendon autografts (n = 5 studies; 75.6% [95% CI, 43.7%-92.5%]). Overall graft failure rate was positively associated with postoperative follow-up time, but this effect was only significant with hamstring tendon autografts ( P < .05). Conclusion: Differences in graft failure rate between patellar tendon and hamstring tendon autografts were not significant. Although follow-up time was only found to have a significant influence on hamstring tendon graft failure rates, this was likely due to the smaller sample of studies assessing patellar tendon graft failures. Differences in return to preinjury activity levels could not be determined due to the lack of studies assessing that outcome. Both patellar and hamstring tendon autografts demonstrate a low risk of failure and moderately high return to activity level after anatomic ACL reconstruction.

Tunnel malposition is one of the most common technical reasons for anterior cruciate ligament reconstruction failure. Small changes in tunnel placement can result in significant differences in outcome. More anatomic placement of the tunnels can lead to greater knee stability and a more accurate reproduction of native knee kinematics. This Technical Note describes 2 tibial tunnel–independent methods to obtain anatomic femoral tunnel placement. The all-inside anteromedial portal technique requires only minimal surgical incisions but allows precise femoral tunnel placement. However, hyperflexion of the knee is required, adequate surgical assistance is necessary, and this technique may be susceptible to graft-tunnel mismatch. The outside-in technique may be more beneficial in obese patients, skeletally immature patients, or revision cases. On the downside, it does require an additional 2-cm surgical incision. This article also provides surgical pearls to fine-tune tibial tunnel placement.

Younger patients and those with smaller hamstring autograft diameters have been shown to be at significantly greater risk of graft failure after anterior cruciate ligament (ACL) reconstruction. To date, there is no information in the literature about the clinical success and/or cost-effectiveness of increasing graft diameter by augmenting with semitendinosus allograft tissue for younger patients.Hybrid hamstring grafts are a cost-effective treatment option because of a reduced rate of graft failure.Cohort study (economic and decision analysis); Level of evidence, 3.We retrospectively identified patients younger than 18 years who had undergone ACL reconstruction by a single surgeon between 2010 and 2015. During this period, the operating surgeon's graft selection algorithm included the use of bone-patellar tendon-bone (BTB) autografts for the majority of patients younger than 18 years. However, hamstring autografts (hamstring) or hybrid hamstring autografts with allograft augment (hybrid) were used in skeletally immature patients and in those whom the surgeon felt might have greater difficulty with postoperative rehabilitation after BTB graft harvest. Patient demographics, graft type, graft diameter, the time the patient was cleared to return to activity, and the need for secondary surgical procedures were compared between the hamstring and hybrid groups. The clinical results were then used to assess the potential cost-effectiveness of hybrid grafts in this select group of young patients with an ACL injury or reconstruction.This study comprised 88 patients (hamstring group, n = 46; hybrid group, n = 42). The 2 groups did not differ in terms of age, sex, timing of return to activity, or prevalence of skeletally immature patients. Graft diameters were significantly smaller in the hamstring group (7.8 vs 9.9 mm; P.001), which corresponded with a significantly greater rate of graft failure (13 of 46 [28.3%] vs 5 of 42 [11.9%]; P = .049). As a result of the reduced revision rate, the hybrid graft demonstrated incremental cost savings of US$2765 compared with the hamstring graft, and the hybrid graft was the preferred strategy in 89% of cases.Driven by increased graft diameters and the reduced risk of revision, hybrid grafts appear to be a more cost-effective treatment option in a subset of younger patients with an ACL injury.

Objectives: Regardless of surgical or conservative management, the majority of patients develop posttraumatic osteoarthritis (PTOA) within 15 years of anterior cruciate ligament (ACL) injury. In addition to MRI or radiographic evidence of cartilage degeneration, the onset of PTOA is associated with increased concentrations of chondrodegenerative and inflammatory biomarkers and reduced Knee Injury and Osteoarthritis Score Quality of Life (KOOS-QOL) scores. Postoperatively, biochemical biomarkers may offer the ability to detect the onset of PTOA earlier than traditional imaging methods; however, little is known about the ability of preoperatively collected biomarkers to predict postoperative symptoms often associated with early onset of PTOA. The purpose of this prospective study was to determine if patient demographics and biomarkers collected on the day of ACL reconstruction could accurately explain the variability in postoperative KOOS-QOL scores. We hypothesized that no combination of biomarkers collected on the day of ACL reconstruction would be associated with 2-year patient-reported outcomes. Methods: Participants included 18 patients (9 females, 9 males; age = 20.1 ± 5.2 years; height = 177.7 ± 11.9 cm; weight = 77.8 ± 18.0 kg) that had previously enrolled in a prospective randomized trial evaluating early anti-inflammatory treatment after ACL injury. As part of the initial trial, synovial, serum, and urinary biomarkers of chondrodegeneration and inflammation were collected on the day of ACL reconstruction. Patients were then contacted to complete patient-reported outcomes 2 years following surgery. A linear regression was performed to determine if a model generated from patient demographics and biomarkers on the day of surgery and could accurately explain the variability in KOOS-QOL scores at 2 years. Results: KOOS-QOL scores significantly improved from 39.9 ± 14.2 on the day of ACL reconstruction to 66.7 ± 19.7 at 2 years (p < 0.001). A model containing urinary CTX-II and sex explained 52% of the variability in 2-year KOOS-QOL scores (adjusted R2 = 0.52, p = 0.002), with higher urinary CTX-II values and female sex associated with poorer KOOS-QOL scores. Urinary CTX-II, which is a biomarker of type II collagen breakdown, individually explained 32% of the variability in 2-year KOOS-QOL scores (p = 0.01) with sex explaining 20% of the variability (p = 0.02). Conclusion: Previous studies have demonstrated that ACL injury triggers a biochemical cascade that worsens over the first 4-6 weeks after injury. The current results demonstrated that higher levels of collagen breakdown as measured via CTX-II levels at the time of surgery was associated with worse KOOS-QOL outcomes at 2 years. This data strongly suggests that initial biochemical changes after injury may have powerful consequences for the injured knee that are not mitigated by surgical stabilization alone. Early anti-catabolic intervention after ACL injury may need to be investigated as an adjunct treatment strategy, particularly in female patients with high CTX-II levels.