Comparative efficacy of an 8-week core stability program versus foot-ankle strengthening on pain, function, and distal structural parameters in individuals with knee osteoarthritis: a randomized controlled trial

Knee osteoarthritis (OA) is a common musculoskeletal condition linked to aberrant joint loading, pain, and reduced function. While effective rehabilitation should target both local knee problems and the entire kinetic chain, direct comparisons between proximal (core stability) and distal (foot-ankle) interventions are limited. This randomized controlled trial evaluated the efficacy of an 8-week core stability exercise (CSE) program versus foot-ankle strengthening (FAS) in individuals with knee OA. One hundred participants (aged ≥ 40 years, Kellgren-Lawrence grade II–III) were randomly assigned to either CSE ( n = 50) or FAS ( n = 50). Both groups performed conventional knee exercises three times weekly for 8 weeks, supplemented by their respective group-specific training. The primary outcome was resting pain intensity evaluated via a visual analogue scale (VAS). Secondary outcomes included the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales, functional performance tests (40-m fast-paced walk, 30-second chair stand, and 11-step stair climb), and distal structural measures (Achilles tendon thickness and navicular/foot ratio). Assessments were conducted at baseline and after 8 weeks, with between-group differences analyzed using ANCOVA adjusted for baseline values. The CSE group showed significantly greater improvements across all outcomes compared to the FAS group. Between-group differences exceeded validated minimal clinically important differences (MCID) for resting pain and all KOOS subscales, met MCID thresholds for the walk and chair-stand tests, and safely surpassed minimal detectable changes (MDC) for the stair-climb test and distal structural parameters; large effect sizes favored core stability training. These findings indicate that proximal core stabilization added to conventional knee exercises provides superior short-term improvements in functional mobility and distal structural surrogates compared to foot-ankle strengthening combined with conventional knee exercises in knee OA rehabilitation. Crucially, these static distal structural modifications are exploratory, likely reflecting localized soft-tissue fluid shifts rather than permanent anatomical remodeling, and demand future validation via advanced diagnostic imaging. Trial Registration: ClinicalTrials.gov ID= NCT06766877 (registered 9 January 2025).