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New Treatment Tool For Ankle Arthritis

Injection of hyaluronic acid into the knee to treat osteoarthritis is an approved treatment now. The Food and Drug Administration (FDA) has given the use of this type of viscosupplementation in the knee a green light. The FDA has NOT approved the use of this viscosupplement for the ankle yet. Why not?

The underlying cause of osteoarthritis in the knee versus the ankle is often different. Experts think this may make a difference in how effective viscosupplementation may be for the ankle. The main difference in cause is trauma: arthritis in the ankle joint is more likely to be caused by trauma. Knee osteoarthritis is usually just that -- arthritis that started in the knee without a history of trauma.

Studies show that viscosupplementation isn't really effective for knee post-traumatic osteoarthritis. So there's no reason to believe (and minimal proof yet) that this type of treatment will work in patients with posttraumatic ankle osteoarthritis. Why not?

No one is exactly sure yet why viscosupplementation works well for primary arthritis affecting the knee but not posttraumatic joint arthritis. Research on hyaluronic acid shows that this substance is the main ingredient in joint synovial fluid. It seems to have many roles. Besides remaining elastic under high shear forces, it also keeps the synovial fluid slippery or viscous.

Lubricating fluid inside the joint makes it possible for the joint to withstand the heat that develops within the joint even with low shear stress. Hyaluronic acid can store mechanical energy for release later when needed. It bathes the cartilage cells with fluid and keeps them nourished. It even has antiinflammatory properties to reduce joint inflammation and an ability to reduce pain -- or at least the perception of pain.

Would injection of hyaluronic acid into the arthritic ankle have these same effects and benefits? Some studies have been done with this treatment for ankle osteoarthritis. But the number of patients involved was small and the results have only been measured for up to six months. The results did show a positive effect of viscosupplement injections when compared with placebo (fake) injections. Some viscosupplements have been given approval in Europe for use with ankle patients.

Research is now underway to test hyaluronic acid in the treatment of ankle osteoarthritis. The hope is to find equal (if not better) results as have been reported with knee viscosupplementation. Minimizing adverse side effects is a secondary goal of current studies. Reports of temporary effects such as pain, warmth, swelling at the injection site have been noted. Up to one third of the patients treated with viscosupplementation experience some type of negative side effect.

When larger studies with more long-term results are available, the FDA may approve the use of viscosupplementation as a treatment tool for ankle osteoarthritis. The complex nature of the joint with its many bones (compared to the single hinge-type knee joint) make it necessary to research this treatment option carefully before approving it for use in the U.S.A.

Jennie McKee. Can Viscosupplementation Ease Ankle OA? In AAOSNow. November 2008. Vol. 2. No. 11. Pp. 1, 9.

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