In vitro systems in the study of osteoarthritis

Osteoarthritis is a widespread disorder of vertebrate synovial joints in which progressive thinning of articular cartilage occurs at focal sites until in severely advanced stages, the underlying subchondral bone is exposed (Lee et al., 1974; Howell et al., 1976; Peyron, 1979). It is common in domestic animals, and in man the highest incidence is in late middle age. Osteoarthritis is diagnosed only at relatively advanced stages of the disease and it may be 20 years or more before clinical signs or radiological changes appear. There are probably a number of predisposing factors, including genetic predisposition but deterioration and abrasion of the articular surface strongly implicates mechanical factors. Formation of new bone at the articular surface and joint margins which accompanies the deterioration of cartilage suggests that the joint is an internally interacting system and that there is no single point in the pathological process (see Sokoloff, 1969). Because of its slow progress, osteoarthrosis is a difficult disease to study and hence its pathogenesis is poorly understood.