Viscosupplementation for the Treatment of Osteoarthritis of the Knee with Hyaluronan and Hylans: Rationale and State of the Art

Hyaluronan is essential in maintaining the homeostasis of joint tissues and synovial fluid through its elastoviscosity, lubricating properties, protection of cells and nerves, molecular sieving effect, and metabolic influence on synovial cells. These properties are molecular weight- and concentration dependent. In osteoarthritis (OA), synovial fluid hyaluronan becomes less effective because of dilution and a decrease in molecular weight. Through viscosupplementation, a therapeutic procedure of serial intra-articular injections of high molecular weight hyaluronan or its derivatives, hylans, the normal elastoviscous properties of synovial fluid may be restored. The reported tolerance of viscosupplementation is very good, with similar results for the three available products. Local adverse effects occur after approximately 2% of the injections in 2%-4% of the patients; these are typically short lived and have no sequelae. This efficacious and safe treatment is the only therapy for osteoarthritis that addresses the mechanorheological homeostasis of joint tissues.