Hip abductor strength in people with knee osteoarthritis: A cross-sectional study of reliability and association with function

• Knee osteoarthritis leads to diminished physical function.
• We found that hip abductor strength was more important than knee extensor strength to function.
• Hip abductor strength can be reliably assessed using a hand-held dynamometer.
• Hip abductor strength should be emphasized in the clinical management of knee osteoarthritis.

BackgroundTo investigate the clinical importance of hip abductor (HA) strength in people with knee osteoarthritis (OA), the purposes of this study were to 1) compare the association of HA strength and physical function to that of knee extensor (KE) strength and physical function, and 2) determine the reliability of the assessment of HA strength using a hand-held dynamometer.MethodsThirty-five individuals [58 years standard deviation 10 years old] with knee osteoarthritis participated. Physical function was assessed with performance-based [Get-Up and Go (GUG), stair climb and descent (SC), and five times chair rise (CR)] and self-reported (WOMAC function) measures. The relationship between strength and function was assessed using bivariate correlation and hierarchical multiple regression models. Reliability across sessions was assessed in 25 subjects.ResultsIn the bivariate models, both KE and HA strength were both significantly associated with performance-based measures of function, but not WOMAC function. After controlling for anthropometric factors and KE strength in the hierarchical models, HA made significant independent contributions to the prediction of GUG and SC, but not CR or WOMAC function. The reliability of HA strength was excellent (ICC2, 3 = 0.94; 95% CI = 0.86–0.97), while the minimum detectable change (MDC95) was 0.29 Nm/kg (95% CI = 0.23–0.41).ConclusionHA strength can be reliably measured and is closely associated with functional performance in people with knee OA.Clinical RelevanceThese results provide preliminary evidence suggesting that HA strength may be an important rehabilitation target for the conservative management of knee OA.