Association Between Preoperative Joint Line Convergence Angle and Clinical Outcomes After Isolated Medial Meniscus Posterior Root Tear Repair

Abstract

Background:

While coronal malalignment influences outcomes after medial meniscus posterior root tear (MMPRT) repair, alignment parameters such as the hip-knee-ankle angle (HKAA) may not fully capture the biomechanical setting of the medial compartment. The joint line convergence angle (JLCA) reflects the intra-articular environment but has not been well studied as a prognostic factor after MMPRT repair.

Purpose/Hypothesis:

The purpose of this study was to evaluate the association between the preoperative JLCA and patient-reported outcomes (PROs) after MMPRT repair and to determine whether the JLCA provides prognostic information independent of the HKAA. It was hypothesized that a higher preoperative JLCA would be associated with inferior postoperative PROs and that the JLCA would demonstrate a stronger association with outcomes than the HKAA.

Study Design:

Case series; Level of evidence, 4.

Methods:

A retrospective review was performed of patients undergoing isolated MMPRT repair by a single surgeon between 2017 and 2025. The preoperative and postoperative JLCA were measured on weightbearing knee radiographs. In a subset of patients with full-length radiographs, the HKAA was also measured, with positive values indicating varus alignment and negative values indicating valgus alignment. PROs included the International Knee Documentation Committee (IKDC) and Knee injury and Osteoarthritis Outcome Score (KOOS)–short scores collected preoperatively and at 24 months postoperatively. Multivariable linear regression models assessed the independent association between the JLCA and postoperative outcomes while adjusting for age, sex, body mass index, baseline scores, intraoperative cartilage status, and HKAA. Receiver operating characteristic analysis evaluated the ability of the JLCA to predict achievement of the minimal clinically important difference.

Results:

A total of 62 patients (mean age, 60.0 ± 11.1 years) were included. Both the IKDC and KOOS-short scores improved significantly at 24 months (both P < .001). A higher preoperative JLCA was significantly associated with lower 24-month IKDC (r = −0.34; P = .008) and KOOS-short (r = −0.36; P = .004) scores. In the multivariable models, each 1° increase in the JLCA corresponded to a 5.45-point decrease in the IKDC score and a 4.35-point decrease in the KOOS-short score (both P < .01). In the subset of patients with full-length radiographs (n = 24), the mean HKAA was 3.1°± 3.4° (range, –2.5° to 14.3°). When both the JLCA and HKAA were included, the JLCA remained independently associated with outcomes, whereas the HKAA did not. The JLCA demonstrated fair discrimination for achievement of the minimal clinically important difference (area under the curve = 0.60-0.69). The mean JLCA increased slightly from 1.90°± 1.37° preoperatively to 2.13°± 1.27° postoperatively (P = .029).

Conclusion:

The preoperative JLCA was an independent predictor of clinical outcomes after isolated MMPRT repair. Incorporation of the JLCA into a preoperative assessment may improve patient counseling and risk stratification and help identify patients who could benefit from adjunctive strategies aimed at optimizing the medial compartment's biomechanical environment.