Mechanisms of persistent synovitis.

Rheumatoid arthritis is characterised by persistent and symmetrical synovitis. In this article we propose two linked hypotheses to explain these observations. A mechanism to explain symmetry of synovitis is described whereby fine afferent nerve fibres from joints become bilaterally sensitized to movement with resultant release of neuropeptides promoting an inflammatory response. Clinical and experimental evidence is reviewed and shows that movement and resulting hypoxic reperfusion injury leads to a persistent synovitis.