Osteoarthritis Progression After Medial Meniscus Posterior Root Repair: An Analysis of Surgical Timing and Baseline Degenerative Severity

Background: Medial meniscus posterior root tears (MMPRTs) disrupt hoop stress transmission, leading to increased contact pressures, extrusion, and accelerated medial compartment osteoarthritis (OA). Although early surgical repair is widely recommended, it remains unclear whether surgical timing independently influences long-term radiographic outcomes after root repair. Purpose: To compare radiographic OA progression after acute (≤3 months from symptom onset) versus chronic (>3 months) MMPRT repair and to determine whether surgical timing independently predicts Kellgren-Lawrence (KL) grade progression after adjusting for baseline degenerative severity. Study Design: Cohort study; Level of evidence, 3. Methods: Patients undergoing isolated arthroscopic transtibial pullout repair for MMPRT between 2016 and 2023 were retrospectively reviewed. Inclusion required preoperative magnetic resonance imaging (MRI) and 2-year postoperative weightbearing radiographs. Patients were categorized as acute or chronic based on time from symptom onset to surgery, rather than confirmed time of tear occurrence. Primary outcome was change in KL grade (ΔKL). Secondary variables included preoperative meniscal extrusion percentage, joint space width, MRI diagnostic signs, mechanical alignment, and International Knee Documentation Committee (IKDC) scores. Multivariable linear regression was used to identify independent predictors of ΔKL progression. Results: In total, 61 patients met the inclusion criteria (acute: 30; chronic: 31). The chronic cohort demonstrated greater unadjusted KL progression (mean ΔKL: 0.65 vs 0.40; P = .049) and higher preoperative meniscal extrusion (47.9% vs 38.7%; P = .030). Multivariable analysis, however, showed that surgical timing (acute vs chronic) was not an independent predictor of ΔKL progression ( P = .31). Instead, meniscal extrusion (β = 0.013, P = .023) and preoperative joint space width (β = −0.194, P = .051) were the strongest predictors of radiographic worsening. Joint space narrowing, MRI signs, mechanical alignment, and postoperative IKDC scores were comparable between groups. Conclusion: Although patients undergoing chronic MMPRT repair demonstrated greater unadjusted radiographic progression compared with those treated acutely, this effect does not persist after controlling for baseline degenerative severity. Osteoarthritis progression after root repair is primarily associated with the preoperative degenerative burden—particularly meniscal extrusion—rather than surgical timing itself. Early diagnosis and referral remain important because delayed presentation is associated with more advanced degeneration at the time of surgery.