Effects of Medial Opening-Wedge High Tibial Osteotomy on 3-Dimensional Knee Joint Biomechanics and Trunk Posture

Background: Knee osteoarthritis (KOA) is a common degenerative condition that leads to pain, disability, and reduced quality of life. Medial opening-wedge high tibial osteotomy (MOWHTO) is a surgical procedure designed to correct alignment and alleviate symptoms by redistributing load. While previous studies have focused on the coronal plane, the impact of MOWHTO on sagittal plane biomechanics and trunk posture remains unclear. Hypothesis/Purpose: The purpose of this study was to evaluate 3-dimensional biomechanical changes in the knee joint and trunk posture after MOWHTO. It was hypothesized that MOWHTO would result in significant biomechanical changes not only in the coronal plane but also in the sagittal plane, along with changes in trunk posture. Study Design: Case series; Level of evidence, 4. Methods: This retrospective study included 55 patients (55 knees) with medial compartment KOA (Kellgren-Lawrence grade ≥2) who underwent MOWHTO. Preoperative and postoperative gait analyses were conducted using a 3-dimensional motion capture system and force plates to assess knee joint kinetics and kinematics including trunk posture. Knee joint moments (knee adduction moment [KAM], knee flexion moment [KFM], and knee rotation moment [KRM]) and total joint moment (TJM), along with relative contributions of each moment, were assessed. Radiographic parameters such as hip-knee-ankle (HKA) angle, percentage of mechanical axis (%MA), and femorotibial angle (FTA) were evaluated. Clinical outcomes were assessed using the Japanese Knee Osteoarthritis Measure and Knee Society Score. Paired t tests were performed for statistical analysis between pre- and postoperative results. A P value <.05 was considered statistically significant. Results: Postoperatively, significant reductions in KAM ( P < .01) and TJM ( P < .001) were observed, with a shift in the proportional contribution from KAM to KFM. KFM remained unchanged pre- and postoperatively. Knee varus angles decreased ( P < .01), and trunk flexion angles significantly decreased, indicating better postural alignment ( P < .01). Radiographic analysis demonstrated increased HKA angles and %MA, along with reduced FTA ( P < .01). Clinical outcomes showed significant pain relief and functional improvement ( P < .01). Conclusion: MOWHTO was associated with significant changes in 3-dimensional gait biomechanics, including knee joint moments and trunk posture, highlighting its comprehensive role in restoring functional alignment in patients with medial compartment KOA, although the case series design may limit generalizability.