A relatively new procedure, called viscosupplementation, injects a preparation of hyaluronic acid into the knee joint. Hyaluronic acid is a naturally occurring substance found in the synovial (joint) fluid. It acts as a lubricant to enable bones to move smoothly over each other and as a shock absorber for joint loads.
People with osteoarthritis (“wear-and-tear” arthritis) have a lower-than-normal concentration of hyaluronic acid in their joints. Viscosupplementation may be a therapeutic option for individuals with osteoarthritis of the knee.
Viscosupplementation has been shown to relieve pain in many patients who cannot get relief from nonmedicinal measures or analgesic drugs. The technique has been used in Europe and Asia for several years, but the U.S. Food and Drug Administration did not approve it until 1997, and then only for treating osteoarthritis of the knee. Several preparations of hyaluronic acid are now commercially available.
Viscosupplementation can be helpful for people whose arthritis has not responded to basic treatments. It is most effective if the arthritis is in its early stages (mild to moderate).