Chronic knee effusions in patients with advanced osteoarthritis: implications for functional outcome of...

Intra-articular injection of exogenous hyaluronan (viscosupplementation) is an effective treatment for knee pain due to osteoarthritis, but the amount of dilution of the viscosupplement by the synovial fluid, which could affect efficacy, has not been previously considered. In this study, the synovial fluid volume was measured in patients with advanced osteoarthritis and the variation in viscosupplement concentration that would have occurred had the patients received that treatment was calculated. A closed aspiration was performed under anesthesia in this consecutive, prospective series of patients undergoing total joint arthroplasty for advanced osteoarthritis. Any remaining synovial fluid was collected by means of open aspiration following an arthrotomy. Overall, 27.0 +/- 15.5 mL (range: 10-70 mL) of synovial fluid was present in the joints. Irrespective of the particular proprietary hyaluronan product, the viscosupplement concentration would have varied by an approximate factor of 6. Interpatient variation in volume of synovial fluid may explain some of the observed variations in efficacy in patients treated with viscosupplementation. Stricter attention to the possibility of a joint effusion and aspiration of the joint where indicated might lead to improved results.