Pathogenesis and epidemiology of osteoarthritis.

Osteoarthritis (OA) is a disease of high prevalence that produces substantial morbidity and is a leading cause of physical and psychological disability and expense, including time lost from work, medical care, and disability support. Until recently, the focus of research into the pathophysiology of OA has been on articular cartilage and has not resulted in either biomarkers of OA activity or effective targets for disease-modifying therapy. The contemporary paradigm of OA considers involvement of all joint tissues. It has been shown that, in later-stage OA, bone blood flow and oxygen content are markedly reduced and have a deleterious effect on bone cells, inducing them to release proteins (cytokines) that contribute to the bone remodeling and cartilage breakdown seen in OA.