Risk of Revision and Patient-Reported Outcomes After ACL Reconstruction: Influence of Concomitant MCL Injury and Graft Choice: Analysis of 35,139 Reconstructions From the Norwegian Knee Ligament Register

Background: Concomitant medial collateral ligament (MCL) injury is common in anterior cruciate ligament (ACL) tears, but optimal management of these injury components remains controversial. Purpose: To compare patient-reported outcome measures and the risk of ACL revision surgery in patients with concomitant MCL injuries (treated operatively and nonoperatively) versus isolated ACL injuries and to assess whether MCL treatment strategy or ACL graft choice influenced outcomes. Study Design: Cohort study; Level of evidence 3. Methods: Data were obtained from the Norwegian Knee Ligament Register. Patients undergoing primary ACL reconstruction (ACLR) between 2004 and 2024 were included for graft-survival analyses, and those operated by December 31, 2022, were eligible for 2-year Knee injury and Osteoarthritis Outcome Score (KOOS) outcomes. Patients with concomitant ligament injuries other than to the MCL, ACL repairs, or those with unknown ACL graft type were excluded. Patients were stratified into isolated ACL and ACL + MCL injury groups. Kaplan-Meier survival analyses (unadjusted), multivariable Cox regression, and linear/logistic regression models were used, adjusted for descriptive data, body mass index, meniscal/cartilage injury, time to surgery, smoking, pivoting sports, graft choice, and baseline KOOS. Results: A total of 35,139 ACLRs were included (2410 ACL + MCL and 32,729 isolated ACL; mean age, 28.6 years). Concomitant MCL injury was not associated with an increased overall risk of ACL revision ( P = .5). However, ACL + MCL patients had lower 2-year KOOS Sport/Recreation (Sport/Rec) scores (−2 points, P = .04) and lower odds of achieving patient acceptable symptom state (PASS) for Sport/Rec. Within the ACL + MCL subgroup, hamstring (Hazard ratio [HR], 2.3; P = .001) and quadriceps autografts (HR, 3; P = .009) were associated with a higher revision risk compared with bone-patellar tendon-bone (BPTB) autograft, particularly when hamstring grafts were combined with nonoperative MCL treatment (HR, 2.4; P = .001). Graft choice did not influence the likelihood of achieving a minimal clinically important difference in KOOS. Conclusion: Concomitant MCL injury did not increase the risk of ACL revision but was associated with inferior KOOS Sport/Rec outcomes and lower odds of achieving PASS at 2 years. In patients with concomitant nonoperatively treated MCL injuries, BPTB autograft was associated with a significantly lower revision risk compared with hamstring and quadriceps autografts.