Hyaluronic acid is found in normal joints as a central component to healthy joint fluid. As joints age, the amount of hyaluronic acid in the joint decreases. A result of this is a loss of resilience in the joint; a loss of shock absorbing capacity in, and lubrication of the joint. Hyaluronic acid injections are sometimes compared to filling a car with oil. This analogy loses some of the nuances of how hyaluronic acid injections may help joints, but it is a helpful picture of how they generally function. They replace the lost oil in the joint.
Hyaluronic acid injections are FDA approved for treating knee osteoarthritis. More and more medical centers are evaluating whether hyaluronic acid injections may be helpful in a variety of other arthritic joints. A recent study by ven den Bekerom and Mulier published in Archives of Orthopedic Trauma Surgery in March, 2007 reported that of 120 patients who were candidates for total hip replacement but who first underwent hyaluronic acid injections, 51% did not progress to a total hip replacement after three years. That means that the injections helped more than 60 patients out of 120 avoid hip replacement surgery for at least three years.
In a randomized, controlled trial, Fufulas et al., published a study in 2003 in the Journal of Bone and Joint Surgery in which 22 patents with hip osteoarthritis were randomized to receive either a hip injection of Nimesulide (a non-steroidal anti-inflammatory drug -- NSAID) or hyaluronic acid. Although a small study, the authors found that the patients treated with the hyaluronic acid injections did significantly better than those treated with Nimesulide.
In a French study published in the March 2009 issue of Arthritis & Rheumatism found that in the 85 patients randomly selected to receive a single injection of hyaluronic acid or a placebo, the researchers found no difference between hyaluronic acid and placebo.
While the results of some studies seem to indicate that hyaluronic acid injections may be helpful for hip osteoarthritis, it is still not FDA approved for this usage and more research needs to be done. As such, most insurance companies will not pay for hyaluronic acid injections in the hip. Since hyaluronic acid can cost hundreds of dollars, the cost is prohibitive for many people -- making wide spread usage of hyaluronic acid injections for hip osteoarthritis unrealistic at this time. If you have hip osteoarthritis, would hyaluronic acid injections help you? Only your doctor can tell you if this might be the case. There are other good treatment options for hip osteoarthritis. I would encourage you to discuss all of your options with your doctor.
Hyaluronic acid injections are being explored for a host of other joints as well. Ongoing research is seeking to evaluate whether they may be effective for ankle osteoarthritis, shoulder osteoarthritis, and thumb (carpometacarpal) osteoarthritis. The rationale for them working in knee osteoarthritis would appear to make them a logical option for osteoarthritis of other joints as well. After all, these mobile joints have the same basic structure, though they do vary in size and function. However, until adequate research has been performed and reported, we won't know for sure if they are effective for these other joints and so further evidence-based recommendations will have to wait. What can be said at this point is that hyaluronic acid injections appear to have the potential to be another conservative therapeutic tool in the physician's toolkit in treating osteoarthritis of a whole host of painful joints. Whether or not this will prove to be the case, and how effective they may be for different joints, is something that only time and good research will tell.