Medial Meniscus Posterior Root Repair Is Associated With Better Function But Persistent Knee Varus Thrust and Reduced Knee Internal Rotation During Gait

PURPOSE: To define gait kinematics and kinetics in patients with medial meniscus posterior root (MMPR) tear and repair, compared with healthy, age-matched controls. METHODS: This was a cross-sectional, observational study conducted between October 4, 2022, and March 3, 2025, and involved 3 distinct groups: individuals with acute or chronic unrepaired MMPR tears, patients who had undergone MMPR repair, and healthy controls matched for age, sex, and body mass index. All individuals in the repair group had previously undergone transtibial pullout repair performed by a single fellowship-trained surgeon at least 6 months before study inclusion (mean: 19.7 ± 14.2; range: 6.0-47.3). Gait analysis was performed using a marker-based 3D motion capture system and force plates. Primary outcomes included knee joint kinematics and kinetics. Statistical comparisons were conducted using discrete kinematic and kinetic data and Statistical nonParametric Mapping to evaluate intergroup differences across the gait cycle. Patient-reported outcomes were also assessed using International Knee Documentation Committee Subjective Knee Form, the Knee Injury and Osteoarthritis Outcome Score Jr., the Veterans RAND 12 Item Health Survey, and Visual Analog Scale pain scores, with Patient Acceptable Symptom State (PASS) reported using previously validated absolute thresholds. Group comparisons were performed using the Kruskal-Wallis test. The significance level was set at 5%. RESULTS: A total of 58 knees were analyzed: MMPR tear (n = 22), MMPR repair (n = 19), and healthy controls (n = 17). Both MMPR tear and repair groups exhibited increased knee varus thrust (Tear: 5.0° ± 2.1; Repair: 5.2° ± 2.0; Control: 3.3° ± 0.9; P < .01), decreased tibial internal rotation at loading response (Tear: -6.2° ± 5.3; Repair: -2.1° ± 3.6; Control: 2.2° ± 5.8; P < .01), and greater knee adduction angle (varus) at midstance (Tear: 0.1° ± 3.9; Repair: -0.1° ± 5.0; Control: -5.9° ± 4.1; P < .01). The MMPR repair group exhibited higher functional scores (International Knee Documentation Committee Subjective Knee Form: 75.3 ± 19.9 vs 43.6 ± 14.2; the Knee Injury and Osteoarthritis Outcome Score Jr.: 84.7 ± 15.4 vs 59.7 ± 8.9; P < .01), lower pain levels (Visual Analog Scale: 1.5 ± 2.1 vs 3.8 ± 2.4; P < .01), and tibial internal rotation compared with the tear group (P < .01). PASS achievement differed significantly between groups (P < .001), with rates of 71.4%-81.0% in the repair group, 10.5%-26.3% in the tear group, and 88.2%-100% in controls. CONCLUSIONS: The repair group showed more favorable clinical (higher PASS rates) and biomechanical characteristics compared with the tear group. However, both tear and repair groups showed knee kinematic and kinetic patterns currently established as biomechanical risk factors for knee OA progression, such as varus thrust. LEVEL OF EVIDENCE: Level III, retrospective comparative case series.