The joint line convergence angle (JLCA) correlates with intra-articular arthritis

Purpose Knees with unicompartmental varus osteoarthritis (OA) usually display a combination of tibiofemoral bony deformity and increased joint line convergence angle (JLCA). The JLCA is a product of intra-articular deformity and lateral soft tissue laxity. This study aims to define the correlation between the JLCA and progression of OA.Methods A retrospective radiological analysis of 501 patients, who underwent either high tibial osteotomy (HTO) or unicompartmental knee arthroplasty (UKA), was performed. The preoperative OA grade was reported based on the Ahlb & auml;ck and the Kellgren-Lawrence (KL). The hip-knee-ankle angle (HKA), the medial proximal tibial angle (MPTA), the mechanical lateral distal femoral angle (mLDFA) and the joint line convergence angle (JLCA) were recorded. The primary outcome was the relationship between the JLCA values and the OA grade. The secondary outcomes were comparing the JLCA and other alignment parameter values between HTO and UKA groups.Results A total of 501 (59.3% females n = 297) cases were included, comprising 293 cases of HTO and 208 cases of UKA. Patients had a mean age of 57.63 +/- 8.97 years, a mean BMI of 28.37 +/- 7.39 kg/m(2). Patients with Ahlb & auml;ck grade 2 represented 49.3% of all patients (n = 247) and patients with KL grade 3 represented 54.7% of all patients (n = 274). A high JLCA was observed in both groups. The reported mean JLCA in the UKA group was 3.69 +/- 2.1 degrees, and in the HTO group was 2.93 +/- 1.82. There was a significant association between the increase in the JLCA and the progression of OA based on both the Ahlb & auml;ck and KL grades (both p values < 0.001). The mean JLCA in patients with Ahlb & auml;ck grades 1 and 4 was 1.48 +/- 1.32 degrees, and 7 +/- 0.93 degrees, respectively. The mean JLCA in patients with KL grades 1 and 4 was 1.77 +/- 1.42 degrees, and 4.89 +/- 1.73 degrees, respectively. The mean recorded preoperative HKA angle in the UKA group was 175.06 +/- 3.08 degrees, and in the HTO group was 173.26 +/- 3.02 degrees, whereas the mean MPTA was 88.63 +/- 1.72 degrees for the UKA group and 89.31 +/- 2.29 degrees for the HTO group.Conclusion The JLCA progressively increases with osteoarthritis progression in patients with unicompartmental varus knee osteoarthritis. The JLCA can potentially be used as a grading parameter for osteoarthritis progression akin to Ahlb & auml;ck and Kellgren-Lawrence grading systems.

Automated summary

This study aims to investigate the correlation between the joint line convergence angle (JLCA) and the progression of osteoarthritis (OA) in patients with unicompartmental varus knee OA. The results showed that an increase in JLCA is closely associated with OA progression.