[Significance of physical activity for bone mass and fracture risk in patients with rheumatoid arthritis].

Subjects with rheumatoid arthritis (RA) have reduced bone mineral density (BMD) and at least a twofold increased risk of osteoporotic fractures. Several factors, including the inflammatory process itself, treatment with glucocorticoids, and physical inactivity have been suggested as being implicated in the aetiology. Only a few studies, however, have examined the value of physical activity for the maintenance of BMD in RA. Cross-sectional studies have shown associations between BMD and indirect measures of physical activity, such as muscle strength and a self-reported degree of physical activity and functional capacity. Only three randomised controlled trials have been performed and none of these were able to demonstrate that exercise had an effect on BMD. Whether physical activity is associated with a reduced risk of fracture has only been addressed in a few cross-sectional studies, which yielded conflicting results, and has not yet been examined in longitudinal trials. Consequently, there is no evidence that physical exercise reduces bone loss and risk of fracture in RA. It is well-known, however, that immobilisation leads to rapid bone loss and should therefore be avoided.