Intra-articular hyaluronan therapy.

The hyaluronan in normal synovial fluid plays an important role in joint homeostasis. It contributes to joint lubrication, buffers load transmission across articular surfaces, provides a renewed source of hyaluronan to joint tissues, and imparts antinociceptive and anti-inflammatory properties to synovial fluid. In osteoarthritis, the molecular weight and concentration of hyaluronan in synovial fluid are diminished. This has led to the proposition that removal of pathologic osteoarthritic synovial fluid and replacement with hyaluronan-based products that restore the molecular weight and concentration of hyaluronan toward normal levels can have beneficial therapeutic effects. This form of treatment for osteoarthritis has been termed viscosupplementation. Within the musculoskeletal community there are diverse opinions, ranging from skepticism to acceptance, about viscosupplementation as a mainstream symptom-modifying osteoarthritis therapy. This review focuses on recent basic and clinical studies dealing with mechanism of action, symptomatic efficacy, safety, and disease modification, and places these studies in context with earlier studies.