Shoulder, elbow and wrist movement impairment--predictors of disability in female patients with rheumatoid arthritis.

To explore and describe how shoulder, elbow and wrist movement impairment and age, disease duration, disease activity and shoulder-upper arm pain are associated with disability in rheumatoid arthritis, these variables were investigated in 63 females. Multiple linear regression analysis indicated that limitations in functional shoulder-arm movement and in active wrist motion ranges explained 30-35% of the variation among the patients' results within each of the physical disability instruments used. The Ritchie index for the upper-extremity might be a predictor of disability, explaining 6-28% of the variation within different disability questionnaires, while shoulder tendalgia explained 24% of the variation in shoulder-arm disability. Altogether, however, our predicting variables only explained 11-30% of the variation in shoulder-arm disability and 25-50% of the variation in the other disability areas studied. Thus, other factors not studied here, e.g. muscle strength and hand grip function, and e.g. psychological and social factors are probably also of importance and remain to be elucidated.