Biomarkers in osteoarthritis

Purpose of review Osteoarthritis is a chronic disease characterized by progressive destruction of articular cartilage and subchondral bone, and synovial reaction. Clinical and radiologic findings that form the basis of the diagnosis of osteoarthritis are poorly sensitive for monitoring the progression of the disease. Biologic markers reflecting quantitative and dynamic changes of joint tissue turnover represent promising adjunct tools. Recent findings New tissue-specific markers have been developed and include assays for type II collagen synthesis and degradation and synovitis. Prospective studies indicate that increased or decreased levels of some of these markers are associated with rapid progression of joint destruction in patients with knee osteoarthritis. Because progression of joint damage is likely to result primarily from an imbalance between degradation and reparative processes, a combination of markers reflecting these two components appears promising. For example, combining two new markers for type II collagen synthesis and degradation in an uncoupling index of cartilage turnover was more effective in predicting 1-year radiologic progression in knee osteoarthritis than the measurement of a single marker. Preliminary data in rheumatoid arthritis show a rapid response of a marker of type II collagen degradation under disease-modifying antirheumatic drugs, with early changes of this marker being predictive of long-term radiologic progression. Summary Recent evidence suggests that the combination of some biologic markers will be useful for identifying patients at risk for rapid joint destruction in osteoarthritis. Because of their rapid changes under treatment, biologic markers will play an important role in the development and monitoring of new structure-modifying therapies for osteoarthritis.