The hip joint, like other joints) contains a small amount of a lubricating gel-like substance called synovial fluid. This fluid contains a component called hyaluronic acid, which can break down, become thinner and less shock absorbing with age. It is not just a viscosupplement but it also interferes with prostaglandins and cytokines, which are naturally occurring compounds that promote inflammation.
Hyaluronic acid can be replaced by injecting into the joint space, with the goal to improve the joint’s gliding motion, providing pain relief in the setting of osteoarthritis. Viscosupplementation with hyaluronic acid works best in the early stages of osteoarthritis. The injections may be done with ultrasonographic guidance. This is because Improper placement of hyaluronic acid can result in increased swelling and discomfort in the joint.
Hyaluronic acid injections have been FDA approved for treating knee osteoarthritis. But they have not been approved for hips or other joints. Nevertheless, it has been used off-label for hip injections at many centers. In other words, using it for hip osteoarthritis is considered to be investigational and not medically necessary. The results from research have been particularly impressive the American College of Rheumatology does not recommend using it for hip osteoarthritis.
Injectable hyaluronic acid was first marketed as Synvisc, and now it is available as Euflexxa, Orthovisc, Hyalgan, and Supartz. Synvisc-One is a single injection formulation and requires a series of three injections.
They may be considered in patients who have pain not adequately controlled by NSAIDs. Hyaluronic injections may not be effective in all patients and the treatment could be repeated, but ideally not more than twice per year. A study done in Australia showed that hyaluronic acid injections reduced pain in an average patient by 28 to 54 percent. This is comparable to the efficacy of NSAIDs taken for osteoarthritis. Researchers are trying to find ways to predict which patients will respond better to hyaluronic acid injections as there is variability in response to it.
They are considered to be better than corticosteroid injections because although the latter provides significant relief within a few days, the pain returned markedly within a month or so. And of course, hyaluronic acid does not have the same side effects as steroids do.
Immediately after the procedure, there may be localized pain, warmth, or swelling, and symptomatic relief can be achieved by applying ice packs. One should avoid putting excessive weight on the hip for the first two days after the procedure. The patient should be counseled that pain relief is not immediate, and could take several weeks to achieve full effect. They should also be informed that the treatment is not curative, as in it will not reverse but slow down the damage to the cartilage from arthritis. They should also be notified about the experimental nature of the treatment and that it has had mixed results at best.