Determinants of physical functioning in women with knee osteoarthritis.

BACKGROUND: Knee osteoarthritis (OA) is an important health problem with its high prevalence and association with pain and functional disability in physical tasks and activities especially in women.

AIMS: To explore the impacts of widely seen demographic, pathological, psychological, and impairment factors on physical functioning in women with knee OA using the performance-based and self-reported measures.

METHODS: One hundred and ten women with knee OA participated in this study. Performance-based measures included the 10-m walk test, timed up and go (TUG) test, and a stair test. Self-reported physical functioning was measured using the Western Ontario and McMasters Universities OA Index. Knee muscle strength, pain intensity, flexion range of motion (ROM), body mass index (BMI), radiographic severity, and anxious and depressive symptoms were measured. Age, disease duration, and comorbidities were recorded. Correlation and linear regression analyses were used to assess the associations.

RESULTS: In the linear regression models, knee muscle weakness, limited knee flexion ROM, pain intensity, and older age contributed to 65% of variance in physical performance measures mostly explained by knee muscle weakness. Knee pain intensity, BMI, anxiety, and knee muscle weakness contributed to 60% of variance in WOMAC physical function score mostly explained by pain. Radiologic severity, depression, comorbidities, and disease duration did not have a significant association (P < 0.05). Performance-based measures had significant but moderate correlations with WOMAC physical function score (r range 0.51-0.57, P < 0.05).

CONCLUSION: In women with knee OA, knee muscle strength was the main determinant of performance-based physical functioning together with knee flexion ROM, knee pain, and age. Knee pain was the main determinant of self-reported physical functioning. BMI, anxiety, and knee muscle strength had some contributions as well. Performance-based and self-reported measures had moderate relations and evaluate different aspects of physical functioning. In the management of women with knee OA strengthening of weak knee muscles, improving limited flexion ROM, pain management, weight loss, and improving anxiety should be considered as a priority and performance-based and self-reported measures should be used together for a comprehensive evaluation of physical functioning.