Decrease in the Postoperative Joint‐Line Convergence Angle of the Contralateral Knee After a Medial Open‐Wedge High Tibial Osteotomy

Purpose To evaluate whether a medial open‐wedge high tibial osteotomy (MOWHTO) influences the change in the joint‐line convergence angle (JLCA) in the contralateral knee. Methods Whole‐leg radiographs of patients who underwent MOWHTO between January 2016 and December 2024 were reviewed, with a minimum follow‐up period of 1 year. Radiographic measurements were analyzed to assess the preoperative and postoperative changes (Δ) in both lower limb parameters, especially JLCA. Patients were divided into 2 groups based on their preoperative (pre‐) JLCA levels at the contralateral knee ( ck ). Group I consisted of knees with a pre‐JLCA ck of <2.0°, while group II included knees with a pre‐JLCA ck of ≥2.0°. Statistical analyses, including paired t tests, χ 2 test, Fisher's exact test, Spearman's correlation, and simple linear regression analysis, were performed using R software. The minimal clinically important difference (MCID) was calculated as one‐half of the standard deviation of pre‐JLCA ck . Univariable and multivariable logistic regression were performed to identify factors independently associated with MCID achievement of ΔJLCA ck . P value < .05 was considered statistically significant. Results A total of 102 knees were included, with 63 knees in group I and 39 knees in group II. Postoperatively, the JLCA ck significantly decreased from 1.8° (95% confidence interval: 1.5°‐2.0°) to 1.3° (95% confidence interval: 1.1°‐1.5°) ( P value = .04). Compared with group I, group II showed a significantly greater reduction in JLCA ck after MOWHTO (0.8°, exceeding an MCID threshold of 0.6°, P < .01), whereas group I showed a reduction of 0.3° ( P < .01). In the multivariable logistic regression model, pre‐JLCA ck ≥ 2° was independently associated with MCID achievement (odds ratio: 7.14, 95% confidence interval 2.60‐21.89, P < .001). Conclusions MOWHTO significantly contributed to a reduction in postoperative JLCA in both the contralateral and operated knees. Additionally, a greater pre‐JLCA ck was associated with a larger ΔJLCA ck . Level of Evidence Level III, retrospective study.