Association between hip extensor muscle weakness and disability of activities of daily living in patients with early-stage knee osteoarthritis

Introduction This study aimed to investigate the association between hip extensor muscle weakness and performance of activities of daily living (ADL) including stair ambulation, sit-to-stand (STS), and walking in patients with early-stage knee osteoarthritis (OA). Methods Community-dwelling older individuals (age ≥ 65 years and Kellgren–Lawrence grade 1–2) were recruited in this cross-sectional study. The ability to perform stair ambulation, STS, and walking was measured using the Japanese Knee Osteoarthritis Measure. The maximum isometric knee extensor and hip extensor muscle strengths were evaluated. To investigate the association between hip extensor muscle strength and performance on ADL, a multivariate logistic analysis was conducted, adjusting for age, sex, and knee extensor muscle strength. Results A total of 161 participants were included in this study. Multivariate logistic analysis revealed a significant association between lower hip extensor muscle strength and higher presence of difficulty in stair ambulation [odds ratio (OR), 0.33; 95% confidence interval (CI), 0.11. 0.98; p < 0.05] and STS (OR, 0.32; 95% CI, 0.11. 0.92; p < 0.05). No significant association between hip extensor muscle strength and difficulty in walking was observed (OR, 0.47; 95% CI, 0.14. 1.62; p = 0.23). Conclusions Hip extensor muscle weakness was associated with difficulty during stair ambulation and STS in patients with early-stage knee OA, after adjusting for knee extensor muscle strength. The results suggest that hip extensor muscle strength may be important to improve or maintain ADL in patients with early-stage knee OA.