Osteoarthritis - one disease or many?

The classical features of osteoarthritis (OA) include osteophytosis,joint space narrowing, subchondral cyst formation, sclerosis, deformity and low-grade synovitis. OA has been tacitly assumed to be a homogeneous disorder and dismissed as "degenerative". This short article will seek to challenge this traditional view and suggest that at least two major processes emerge from detailed radiological studies in patients with OA. One comprises osteophytosis associated with hyaline cartilage thinning and perhaps joint instability. This may represent a normal response to joint instability, and be seen as a healing mechanism. The other, when subchondral sclerosis and bone attrition predominate, may reflect joint failure.