Q: I had some special injections to my knee for arthritis that helped smooth things out and improve pain and motion. It was expensive but my insurance company paid for it (well they paid the usual 80 per cent). I asked about having the same treatment for my ankle arthritis and they flat refused to pay. What's up with that? Can I fight it?

A: It sounds like maybe you had a series of injections using hyaluronic acid. Hyaluronic acid is a substance naturally found in the body in small quantities. It seems to have a role in the multiplication of normal, healthy cartilage cells. Used as an injection into the joint, it is designed to rebuild the protective joint cartilage.

Fifteen years ago, the Food and Drug Administration (FDA) approved the use of an injection of hyaluronic acid for knee arthritis. It has been used ever since for the effective relief of arthritis pain in some carefully selected patients.

Now surgeons are turning their attention to the possible use of this same injection for ankle arthritis. Although it has not yet been approved for this type of use by the FDA, studies are starting to trickle in. From what has been reported so far, there isn't a clear benefit to these injections for the ankle. In fact, according to one random controlled trial, hyaluronic acid didn't work any better than a placebo injection using saline (salt) solution.

The question comes up: why do hyaluronic acid injections seem to work so well for some patients with knee osteoarthritis but patients with ankle arthritis don't't get the same benefit? It's possible that because most ankle arthritis is the result of trauma (and knee arthritis is not), there is a difference in the response to hyaluronic acid. Ankle cartilage is also a lot stiffer, denser, and less elastic compared with knee cartilage. Maybe that makes a difference.

Until there is enough evidence that hyaluronic acid is an effective treatment for ankle arthritis, it is unlikely that insurance companies will reimburse for its use. With the high cost of this product, further study is needed to find new types of nonsurgical treatment for ankle osteoarthritis that are cost effective and economical.

Reference: Henry DeGroot III, MD, et al. Intra-Articular Injection of Hyaluronic Acid is Not Superior to Saline Solution Injection for Ankle Arthritis. In The Journal of Bone and Joint Surgery. January 2012. Vol. 94A. No. 1. Pp. 2-8.