Altered motor function during daily activities in patients eligible for high tibial osteotomy is primarily driven by knee varus deformity.

Aims: Patients with knee osteoarthritis (OA) and varus deformity present altered gait parameters, especially a large knee adduction moment that is predictive of OA progression. The distinct role of each coexisting parameter, such as OA grade, varus deformity, and previous meniscectomy, in the setting of high tibial osteotomy is not clear. Therefore, the aim of this study was to analyze the motor function parameters in patients eligible for high tibial osteotomy during walking, stair ascending, and stair descending, and to evaluate the effect of OA grade, varus deformity, and meniscectomy. Methods: A total of 52 patients with knee OA and varus deformity participated in this study, including 22 with previous partial meniscectomy, alongside 20 healthy controls. Imaging and motion-capture data during walking, stair ascending, and descending were acquired. Subject characteristics, joint kinematics, joint kinetics, and electromyography on-off activities were compared to evaluate statistically significant differences between the patients and healthy groups. Additionally, multiple linear regression evaluated the relationships between OA grade, varus deformity, and previous meniscectomy with motor function parameters. Results: The patients group showed significantly higher knee adduction and rotation moments, lower hip adduction and ankle inversion, and higher knee adduction and trunk flexion compared with the healthy group, as well as significantly increased biceps femoris activity. In addition, larger varus deformity showed a more marked effect on the major motor function parameters compared with OA grade and previous meniscectomy, especially during walking. Conclusion: Patients eligible for high tibial osteotomy move with altered motor function during daily activities, and the coexisting factors of OA grade, varus malalignment, and previous meniscectomy have different impacts, with varus deformity primarily affecting motor function. These findings help to detect the target that should be considered priority in the treatment of high tibial osteotomy, and highlight the importance of realigning the lower limb to possibly restore motor function.