[3H]proline incorporation in vivo in capsular tissues and menisci during the development of osteoarthritis. An experimental study with rabbits.

In an effort to clarify factors related to the pathogenesis of experimental osteoarthritis, biochemical alterations were studied in articular soft tissues of adult rabbits through the immobilization of the knee of the hind leg in extension for 3, 7, 11, 18, 35 or 56 days. The medial collateral ligament and medial meniscus of the knee, as well as the joint capsule of the hip, were analysed. Total protein synthesis (measured by [3H]proline incorporation) increased in the immobilized legs in all of the tissues examined. The collagen synthesis rate (estimated by specific radioactivity of hydroxyproline) in the medial collateral ligament was enhanced, whereas the collagen content (measured as hydroxyproline concentration) of the tissue declined temporarily. This observation suggests that the collagen degradation rate transiently exceeds that of collagen synthesis. The results indicate that distinct biochemical alterations occur in the periarticular tissues during the early phases of immobilization-induced osteoarthritis. It is of interest that biochemical changes similar to those of the immobilized leg were seen, to a lesser extent, in the structures of the contralateral nonimmobilized leg.