The effect of intensive exercise on disease activity in rheumatoid arthritis (RA) is an interesting one.1 Although we would not dispute that such exercise does indeed have a beneficial effect on parameters of disease activity, we wish to propose an alternative hypothesis as to its mechanism. In particular, we would argue that the effect of raised intra-articular pressure on synovial blood flow during exercise is not as the authors suggest.

The intra-articular pressure in chronically inflamed joints undoubtedly rises during exercise, and exceeds capillary perfusion pressure within the synovium.2 ,3 This pressure rise occurs in joints with and without effusions. …