Effects of intraarticular corticosteroid and sodium hyaluronate injections on synovial fluid production and synovial fluid content of sodium hyaluronate and proteoglycans in normal equine joints.

Hyaluronate and cartilage proteoglycan fragments in synovial fluid from normal equine joints were determined after repeated intraarticular injections of beta-methasone, methylprednisolone, hyaluronate, saline and a combination of beta-methasone + hyaluronate and methylprednisolone + hyaluronate. The experimental intraarticular treatments were given at the beginning of the study and after one and two weeks. Synovial samples were obtained at the onset of the study and after 1, 2, 3, 4, 6, and 8 weeks. The synovial volume was determined and showed no significant changes after the repeated arthrocenteses and the experimental treatments. Corticosteroid injections resulted in increased levels of hyaluronate in the synovial fluid which indicated a stimulatory effect on the synoviocytes to produce hyaluronate. The corticosteroids also resulted in high levels (up to 20 times the initial level) of proteoglycans which indicated joint cartilage degradation. A combined injection of corticosteroids and high molecular weight hyaluronate reduced proteoglycan breakdown which indicated a protective effect of hyaluronate on the articular cartilage.