Determinants of physical function in rheumatoid arthritis: association with the disease process.

Rheumatoid arthritis (RA) is a chronic, debilitating disease that follows a progressive course characterized by persistent inflammation and erosive joint damage leading to functional disability. The Health Assessment Questionnaire is now viewed as a key instrument to measure physical function, based on its reliability and ease of use. It has been demonstrated that multiple variables affect physical function, of which those most frequently indicated are disease activity, joint damage and the psychosocial characteristics of the patient. When these variables are pooled together the variation observed in a patient's physical function over the long term can be explained mainly by disease activity, partially by joint damage and additionally by psychosocial factors. Therefore, to maintain or improve physical function in long-standing RA, it is imperative to control disease activity and joint damage by early initiation of treatment.