Orthopedics · Medical Literature
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.
Abstract
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).
Clinical relevance
Knee osteoarthritis (KL grade II–III) affects a large proportion of adults ≥40 years and is a leading cause of functional disability; optimal kinetic-chain targeting in rehabilitation remains debated. This RCT directly compares proximal (core stability) versus distal (foot-ankle) adjunctive exercise strategies atop conventional knee rehabilitation—a clinically relevant gap given the variety of physiotherapy protocols in current practice. The findings are timely as guidelines increasingly emphasize individualized, mechanism-driven exercise prescription for knee OA.
Key findings
1. Primary outcome – Resting pain (VAS): The core stability exercise (CSE) group demonstrated significantly greater pain reduction than the foot-ankle strengthening (FAS) group after 8 weeks, with between-group differences exceeding the validated MCID for resting pain (exact effect sizes favored CSE; specific VAS point differences and CIs not reported in the abstract). 2. Patient-reported function (KOOS): Between-group differences exceeded the validated MCID across all KOOS subscales (symptoms, pain, ADL, sport/recreation, QoL), with large effect sizes favoring CSE—precise subscale scores and 95% CIs were not itemized in the abstract. 3. Functional performance – 40-m fast-paced walk & 30-second chair stand: Between-group differences met MCID thresholds for both tests in favor of CSE, indicating clinically meaningful gains in mobility and lower-limb muscle endurance. 4. Functional performance – 11-step stair climb: CSE surpassed the minimal detectable change (MDC) for this test, though the between-group difference did not reach the MCID threshold; improvement was nonetheless statistically and practically significant. 5. Distal structural parameters – Achilles tendon thickness and navicular/foot ratio: Both measures showed between-group differences safely exceeding MDC thresholds, favoring CSE; however, authors caution these are exploratory findings likely reflecting localized soft-tissue fluid shifts rather than true anatomical remodeling. 6. Study design: N=100 (CSE n=50, FAS n=50), aged ≥40 years, KL grade II–III, 8-week intervention (3×/week), all groups received conventional knee exercises; between-group analysis conducted via ANCOVA adjusted for baseline values. No specific p-values, CIs, or NNT/NNH were reported in the abstract.
Practice implications
For adults aged ≥40 with symptomatic knee OA (KL grade II–III), adding an 8-week core stability exercise program (3 sessions/week) to conventional knee rehabilitation appears superior to adding foot-ankle strengthening for achieving clinically meaningful short-term reductions in resting pain and improvements across all KOOS domains and functional performance benchmarks; clinicians should consider prioritizing proximal core stabilization as the preferred kinetic-chain adjunct. Patient selection should focus on those with KL grade II–III disease who have not yet optimized proximal neuromuscular control, as this subgroup appears to derive the greatest benefit within this trial's scope. Observed changes in distal structural surrogates (Achilles tendon thickness, navicular/foot ratio) should not be used to guide clinical decision-making at this time, as they are exploratory and require validation with advanced diagnostic imaging before being incorporated into practice.