Time-Course of Knee Muscle Strength Recovery at 3, 6, and 12 Months Postoperatively After Open Wedge High Tibial Osteotomy: Differential Recovery Patterns of Maximal Power and Muscle Endurance

<b>Objectives:</b> This study aimed to evaluate longitudinal changes in knee muscle strength following open wedge high tibial osteotomy (OWHTO) for medial compartment knee osteoarthritis with varus deformity, with particular emphasis on differences between the operated and non-operated knees. <b>Methods:</b> This retrospective study included 78 patients who underwent OWHTO. All patients followed a standardized rehabilitation protocol consisting of protected weight-bearing for six weeks, followed by closed kinetic chain exercises and subsequent open kinetic chain exercises from three months postoperatively. Isokinetic knee extension and flexion strength were assessed preoperatively and at 3, 6, and 12 months postoperatively using a Biodex System IV dynamometer at angular velocities of 60°/s and 180°/s. Absolute muscle strength values and inter-limb strength deficits were analyzed. Statistical analyses were performed using the Shapiro-Wilk, Friedman, and Wilcoxon signed-rank tests, with significance set at <i>p</i> ≤ 0.05. <b>Results:</b> At 60°/s, knee extensor and flexor strength deficits significantly increased after surgery, peaking at three months postoperatively, and gradually improved; however, deficits remained significantly greater than preoperative values at one year (<i>p</i> < 0.05). Similar trends were observed at 180°/s, although they did not reach statistical significance. These deficits were primarily attributable to reduced muscle strength in the operated knee, while strength in the non-operated knee remained unchanged throughout follow-up. <b>Conclusions:</b> Knee muscle strength in the operated limb markedly declined during the first three months following OWHTO, particularly in maximal power, and generally required more than six months to recover toward preoperative levels. These findings emphasize the importance of targeted postoperative rehabilitation strategies focusing on early muscle power recovery after OWHTO.