Differential effects of bleeds on the development of arthropathy - basic and applied issues.

Haemophilia is characterized by a spontaneous bleeding tendency, affecting mainly the synovial joints. Recurrent joint bleeds induce a cascade of inflammatory as well as degenerative processes injuring synovium, cartilage and bone. These processes affect each other and may occur in parallel and/or sequentially. Clinically, the effects of joint bleeds are heterogeneous. A marked variability in joint damage is observed in patients with a similar bleeding history. Also late stage effects differ with some patients developing chronic synovitis, and others suffering from osteochondral degeneration called haemophilic arthropathy. This article reviews the current understanding of the pathogenesis of blood-induced joint damage, elaborates on potential explanations for the differential effects of a bleed, and discusses challenges for future research.