[Current knowledge in the etiology of arthritis]

Osteoarthritis (OA) is a disease process with common risk factors and a variable outcome. The disease process that leads to OA includes factors that are driving degradation in focal areas of articular cartilage and attempted repair processes in the cartilage, subchondral bone, and soft tissues. The individual risk factors for OA lead to a generalized predisposition to the condition, and, together with factors resulting in abnormal biomechanical loading at specific joint sites, they result in disease. There is not only progress in researching etiologic factors in OA (recently discovered collagen type II gene mutations), but there has been considerable progress in recent years regarding the fine details of matrix degradation and its regulation. One is the finding of a hypermetabolic state of matrix turnover early in OA, suggesting an accelerated damage to the newly synthesized molecules over what is observed in healthy cartilage. This sustained damage of matrix molecules slowly leads to a loss of tissue. Further recently elucidated biochemical and biomechanical factors will be discussed.