One-Stage Versus Two-Stage ACL Reconstruction with Concomitant MCL Surgery in Combined ACL and MCL Injuries: A Minimum 2-Year Follow-Up Study.

Background: The optimal timing and staging of anterior cruciate ligament reconstruction (ACLR) in patients with concomitant medial collateral ligament (MCL) injury remain controversial. This study aimed to compare clinical outcomes between a one-stage ACLR group and a two-stage ACLR group in patients with combined ACL and MCL injuries in which the MCL was surgically managed. Methods: This retrospective study included 68 patients with combined ACL and grade III MCL injuries treated with ACLR and MCL surgery. Patients were divided into the one-stage ACLR group (n = 42) and the two-stage ACLR group (n = 26) according to the timing and staging of ACLR relative to MCL surgery. Clinical outcomes, including knee stability, patient-reported outcomes, and range of motion (ROM), were compared between groups. Results: After a minimum 2-year follow-up, both groups demonstrated significant improvements in clinical and stability outcomes, with enhanced anterior knee stability, improved patient-reported outcomes, and better objectively assessed knee function. No significant differences were found between groups in anterior, valgus (one-stage: 1.8 ± 1.1 mm, two-stage: 2.3 ± 1.3 mm; p = 0.160), or rotational stability. Likewise, there were no significant differences in mean flexion deficits (one-stage: 2.6 ± 4.1°, two-stage: 1.0 ± 2.0°; p = 0.137), mean extension deficits (one-stage: 1.5 ± 2.5°, two-stage: 1.3 ± 2.0°; p = 0.137), flexion deficits ≥10° (one-stage: 9.5% [4/42], two-stage: 0%; p = 0.290), extension deficits ≥ 5° (one-stage: 9.5% [4/42], two-stage: 3.8% [1/26]; p = 0.642), or additional procedures for postoperative stiffness (one-stage: 16.7% [7/42], two-stage: 11.5% [3/26]; p = 0.730). Patient-reported outcomes, including the Lysholm and IKDC subjective scores, were also comparable between groups. Conclusions: Both the one-stage ACLR group and the two-stage ACLR group for surgically managed combined ACL and MCL injuries yielded comparable clinical and stability outcomes, suggesting that one-stage ACLR can be performed without an apparent increase in the risk of postoperative stiffness or ROM limitations. However, given the limited sample size, these results should be interpreted cautiously because the study may have been insufficiently powered to detect small clinically meaningful differences.