Hyaluronate for the Treatment of Ankle Osteoarthritis

Ankle osteoarthritis (OA) is a degenerative joint disease that can cause substantial pain, muscle weakness and functional limitations. Due chiefly to its post-traumatic origin and appearance in young patients, ankle OA has a high impact on socioeconomics and patients’ quality of life. Approximately 6% to 13% of all cases of OA involve the ankle joint (Thomas and Daniels, 2003). Recent research also identify that a larger number of patients are being diagnosed with ankle OA (Saltzman et al, 2005). Currently, no curative therapy is available for OA, and thus the overall goals of management are to reduce pain and prevent disability. Treatment options include simple analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs), weight reduction, physical and occupational therapy, activity modification, orthotic devices, shoe modifications, intraarticular corticosteroid injections, and surgery. Although some cases can be treated successfully with surgery, many patients are either not good candidates for surgery or may want to avoid or delay it if possible. There is a need for a treatment that reduces chronic joint pain and improves function yet avoids toxic effects of medications and the morbidity and mortality risks of surgery. One such option for these patients may be the intraarticular injection of hyaluronate. Hyaluronate, a high molecular weight polysaccharide, is a principal component of synovial fluid and extracellular matrix of articular cartilage. It contributes to the elasticity and viscosity of synovial fluid. In addition to providing joint lubrication and shock absorbancy, hyaluronate helps to maintain the structural and functional characteristics of the cartilage matrix. It also inhibits the formation and release of prostaglandins, induces proteoglycan aggregation and synthesis, and modulates the inflammatory response (Frizziero, 1998). In OA, the concentration and molecular weight of hyaluronate are reduced, limiting its role in maintaining normal joint biomechanics (Engström-Laurent A, 1997). Viscosupplementation with intraarticular injections of hyaluronate was approved by the Food and Drug Administration (FDA) in 1997 for treating pain associated with knee OA. Although the exact mechanism of action is not understood with certainty, recent research suggests that it exerts anti-inflammatory, analgesic, anabolic and possibly chondroprotective effects on the articular cartilage and joint synovium that reduce pain and disability and improve joint function.