High tibial osteotomy leads to medial-lateral redistribution of knee internal forces during walking and stair ambulation and improves patient-reported outcomes.

PURPOSE: This study aimed to evaluate changes in medial and lateral knee contact forces during walking, stair ascent and stair descent following open-wedge high tibial osteotomy, and to assess their association with changes in patient-reported symptoms and function. METHODS: Fifty-two patients with medial knee osteoarthritis and varus malalignment were recruited and subdivided into two groups according to a partially randomised patient-preference design. Three patients dropped out at follow-up, resulting in a cohort of 49 patients who underwent either high tibial osteotomy (n = 25) or conservative treatment (n = 24). Motion capture and radiographic data, as well as patient-reported outcome measures (knee injury and osteoarthritis outcome score KOOS and visual analogue scale VAS), were collected pre- and post-treatment at an average 17.8-month follow-up. Personalised computational models of the musculoskeletal system incorporating tibiofemoral alignment and joint space narrowing were used to estimate medial, lateral and total knee contact forces during walking, stair ascent and stair descent. Changes in joint forces and their distribution were statistically analysed and correlated with changes in the patient-reported outcome measures. RESULTS: High tibial osteotomy led to a consistent redistribution of knee contact forces from the medial to the lateral compartment, with mean reductions in medial forces of up to 0.50 body-weight and mean increases in lateral forces of up to 0.65 body-weight (p < 0.001), across all activities. Conservative treatment resulted in no significant changes. Patient-reported outcomes improved significantly following surgery; however, only weak associations were observed between changes in knee internal loading and improvements in symptoms or function. CONCLUSIONS: High tibial osteotomy effectively unloads the knee medial compartment and redistributes knee internal loads between the medial and lateral compartments during walking and stair tasks. However, the limited correlation with subjective recovery suggests that additional factors beyond load redistribution likely influence clinical outcomes. LEVEL OF EVIDENCE: Level I, randomised controlled trial.