ABC of Rheumatology: OSTEOARTHRITIS

Osteoarthritis is the commonest condition to affect synovial joints, the single most important cause of locomotor disability, and a major challenge to health care. Previously considered as a degenerative disease that was an inevitable consequence of aging and trauma, osteoarthritis is now viewed as a metabolically dynamic, essentially reparative process that is increasingly amenable to treatment. There is no generally accepted definition of osteoarthritis, but most would agree that pathologically it is a condition of synovial joints characterised by focal cartilage loss and an accompanying reparative bone response. Defining this in practice is less easy. Current definition of clinical cases hinges on detecting structural changes clinically or in radiographs. For many the plain radiograph remains the best means of assessment, with evidence of cartilage loss (joint space narrowing) and bone response (presence of osteophytes and sclerosis) being the main criteria. This definition, however, excludes joints with early minimal change, ignores tissues other than cartilage and bone, and omits consideration of biological consequences (symptoms and disability). There is often considerable discordance between structural change and clinical outcome; patients with apparent structural catastrophe may have few or no symptoms. Better understanding of the causes of symptoms and disability is currently a key challenge. Observations about osteoarthritis have led to the suggestion that it is an aspect of the inherent repair process of synovial joints: