OBJECTIVE: To study the extent to which muscle strength and performance, pain, 
and disease activity are associated with the total Health Assessment 
Questionnaire (HAQ) disability index and its subdimensions in male and female 
patients with rheumatoid arthritis.
METHODS: HAQ for functional capacity was completed by 135 patients with 
rheumatoid arthritis referred for orthopaedic surgery (74% women; mean (SD) age 
62 (10) years; disease duration 19 (13) years, 70% positive for rheumatoid 
factor). Knee extension, trunk extension and flexion, grip strength, walking 
speed, and sit-to-stand test were measured to mirror physical function. 
Radiographs of hands and feet, pain, and the modified 28 joint disease activity 
score (DAS28) were also assessed.
RESULTS: Mean total HAQ was 1.08 (0.68) in women and 0.67 (0.70) in men (p = 
0.0031). Women had greater disability than men in five of the eight 
subdimensions of the HAQ. Grip strength was 48%, knee extension strength 46%, 
trunk extension strength 54%, and trunk flexion strength 43% lower in women than 
in men. Knee extension strength was inversely correlated with walking time (r = 
-0.63 (95% confidence interval, -0.73 to -0.51)) and with sit-to-stand test (r = 
-0.47 (-0.60 to -0.31)). In an ordered logistic regression analysis in female 
rheumatoid patients, DAS28, pain, knee extension strength, and grip strength 
were associated with the total HAQ disability index.
CONCLUSIONS: Women reported greater disability than men both in the total HAQ 
and in the majority of its eight subdimensions. In addition to disease activity 
and pain, muscle strength has a major impact on disability especially in female 
rheumatoid patients.