Viscosupplementation: Hyaluronic Acid Injections in the Knee

When osteoarthritis attacks a joint, the level of hyaluronic acid decreases, affecting the joint's lubrication abilities. A series of injections containing hyaluronic acid into the knee joint produces significant pain relief in many patients. The process is known as viscosupplementation.

Exactly how viscosupplementation improves the arthritic knee joint remains a bit of a mystery. Although the injected hyaluronic acid only remains in the knee joint for a few days, pain relief after knee injections can last as long as a year. One theory suggests that the injection stimulates the knee joint to produce more hyaluronic acid, which naturally improves knee lubrication.

 

Another theory is that the injection has anti-inflammatory effects on the knee joint, and that as inflammation declines, so too does the pain level in the knee. Whatever the reason, the fact that knee injections help many arthritis sufferers is well documented.

Two forms of hyaluronic acid are used with viscosupplementation: Synvisc® and Hyalgan®. Hyalgan is a solution of naturally occurring sodium hyaluronate. Synvisc is a synthetic version of the acid, and remains in the joint for a longer period of time than Hyalgan. The long-term pain relief of both Synvisc and Hyalgan appear to be about equal, however.

Knee injections have relatively few side effects. Localized pain that lasts for a few days is not uncommon. A few incidences of pseudogout occurring after the injections have been reported. But, whether this has been caused by the contents of the injection or by the injection itself is unclear. In either case, the incidence was very low.

 

The most unpleasant aspect of knee injections may be the price: Viscosupplementation is an expensive therapy. Fortunately, many health policies do cover the costs of hyaluronic acid injections.

In addition to hyaluronic acid injections, osteoarthritis of the knee is sometimes treated with injections of anesthetic. These numb the knee and provide pain relief for a few days, or even a few weeks at a time. The anesthetic is often combined with corticosteroids to extend the pain relief period.

Wen, D.Y. (2000, August 1). Treating knee osteoarthritis with injections. American Family Physician 62(3), 572.