Clinical outcome in patients undergoing ACL reconstruction in the presence of concomitant MCL injury: a systematic review and meta-analysis

Abstract

The purpose of this study was twofold: (1) to compare clinical outcomes between operative versus non-operative management of concomitant medial collateral ligament (MCL) and anterior cruciate ligament (ACL)injuries, and to compare clinical outcomes between patients with isolated ACL rupture versus combined ACL+MCL injuries. Following PRISMA guidelines, we systematically searched PubMed, Embase, Scopus, Web of Science, and Cochrane CENTRAL up to June 2025. Outcomes included the International Knee Documentation Committee (IKDC) score, Lysholm score, Tegner activity scale, Knee Injury and Osteoarthritis Outcome Score (KOOS), and return-to-sport. Both randomized controlled trials (RCTs) and non-randomized studies of interventions (NRSIs) were included. A meta-analysis was conducted using Stata version 17 to calculate weighted mean differences (WMDs) and assess heterogeneity (I 2 ). Risk of bias was assessed using ROB-2 for RCTs and ROBINS-I for NRSIs. From 2,796 records, 21 eligible studies were identified, of which 12 studies were included in the meta-analysis. Non-operative MCL management showed no significant differences vs. surgery in IKDC (WMD − 1.30, 95% CI − 4.91 to 2.31) or Lysholm (WMD 0.30, 95% CI − 6.39 to 6.98), with trends favoring non-operative management. Combined ACL+MCL injuries achieved near-equivalent performance to isolated ACL in Tegner (WMD − 0.36), IKDC (WMD − 1.45), and Lysholm (WMD − 0.46), but all trended toward isolated ACL superiority. Notably, ACL+MCL had significantly worse KOOS-symptom (WMD − 3.0, 95% CI − 4.9 to − 1.1) and KOOS-QOL (WMD − 6.29, 95% CI − 9.52 to − 3.06). Surgery and non-surgery MCL management in combined ACL+MCL injuries yield comparable functional outcomes, but due to substantial to high heterogeneity (I 2 ranging from 57.95 to 98.61% across analyses), small study numbers (n=2–5), and lack of grade-stratified data, no definitive recommendation for selective surgery can be made. Combined injuries show worse KOOS-symptom/QOL versus isolated ACL. Most studies did not differentiate between MCL tear grade and valgus instability (mm). Importantly, outcomes were not stratified by MCL injury grade; therefore, the finding of comparable results between operative and non‑operative management should not be extrapolated to grade‑specific treatment decisions (e.g., for grade III injuries)