Changes in contralateral knee adduction moment and their biomechanical determinants following valgus high tibial osteotomy for medial knee osteoarthritis.

Abstract

Valgus high tibial osteotomy (HTO) reduces medial knee loading in the operated limb; however, its biomechanical influence on the contralateral knee remains unclear. This study aimed to determine the biomechanical factors associated with changes in contralateral knee adduction moment (KAM) following medial opening wedge HTO (MOWHTO). A total of 46 limbs that underwent MOWHTO were evaluated with three-dimensional gait analysis preoperatively and at 2 years postoperatively. Contralateral KAM, trunk lean angle, shank adduction angle, and lower-limb alignment (%mechanical axis: %MA) were measured. Determinants of postoperative changes in contralateral KAM were identified using regression models that considered alignment changes in both the operative and contralateral limbs, as well as contralateral kinematic parameters. Group-level contralateral KAM did not change significantly after HTO (2.50 vs 2.36 %Nm/(BW × Ht), P = .37). However, individual changes varied ranging from -2.4 to +1.5 %Nm/(BW × Ht). Regression analysis showed that greater alignment correction of the operated limb (P = .03), increased trunk lean toward the operated side (P = .07), and greater contralateral shank adduction angle (P = .10) were associated with increased contralateral KAM. Contralateral KAM exhibited marked individual variability despite the absence of a significant group-level change. Alignment correction, trunk mechanics, and contralateral shank adduction were identified as key determinants of postoperative increases in contralateral KAM. Because even small increases in KAM can contribute to elevated medial knee loading, the individual change may have clinical relevance. These findings emphasize the importance of considering bilateral lower-limb biomechanics when planning and evaluating HTO.