Joint stiffness secondary to immobilization was inhibited by intra-articular hyaluronic acid injection in an experimental joint contracture in rabbits. Biochemical and biomechanical parameters were used to evaluate the joint stiffness after nine weeks of immobilization. In all treatments, hyaluronic acid reduced the measured stiffness in the contracture by approximately 50% as compared to the contractures of the untreated rabbits. In addition, hyaluronic acid prevented the loss of glycosaminoglycans (GAGs) (as measured by hexosamine), which normally occurs in untreated contractures. The results are related to a working hypothesis that intra-articular injections of drugs such as hyaluronic acid (Healon-R) will stimulate hyaluronic acid synthesis within the matrices of periarticular connective tissue (PCT). If the spacing and lubricating properties of the glycosaminoglycans could be maintained in the stress-deprived state, the “centripetal collapse” of the fibrillar matrix could be avoided, anomalous cross-links could be minimized, and more normal joint mechanics could be retained.
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