Joint line convergence angle is the most associated alignment factor with the severity of medial knee osteoarthritis

Abstract Purpose The purpose of this study was to evaluate the relationship between the joint line convergence angle (JLCA) and the severity of medial knee osteoarthritis (OA). We hypothesise that JLCA is the most associated factor with the severity of medial knee OA. Methods This retrospective study included a total of 202 knees that underwent either high tibial osteotomy or medial meniscus repair/partial resection. Kellgren–Lawrence grade and hip–knee–ankle angle (HKAA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA) and JLCA were assessed from preoperative radiographs. Medial meniscus extrusion (MME) was measured using preoperative magnetic resonance imaging. The International Cartilage Research Society (ICRS) grade on the medial femoral condyle and medial tibial plateau were also assessed. The relationships between JLCA and Kellgren–Lawrence grades and MME and ICRS grades were analysed using Spearman's correlation test and regression analysis. Results The JLCA was correlated with the Kellgren–Lawrence grade ( R = 0.765, p < 0.001), MME ( R = 0.638, p < 0.001), ICRS grade on the MFC ( R = 0.586, p < 0.001) and the MTP ( R = 0.586, p < 0.001). Regression analysis showed that age ( p = 0.002) and JLCA ( p < 0.001) were associated with Kellgren–Lawrence grade. Furthermore, JLCA was related to ICRS grade on the MFC ( p < 0.001) and MTP ( p < 0.001). Conclusion The JLCA, reflecting radiological severity, meniscus status, and cartilage lesion, was the most associated alignment parameter in the severity of medial knee OA. The JLCA may be beneficial for quantitative assessment of medial knee OA. Level of Evidence Level III, retrospective cohort study.