Hyaluronic acid Intra-Articular Joint Injections
Hyaluronic acid (HA) is a natural gel-like, lubricating substance that occurs in your joint fluid and cartilage, acting as a shock absorber and lubricant. However, the acid appears to break down in people with osteoarthritis (OA). Injections of hyaluronic acid directly into the knee joint are selectively used in the treatment of OA. Most people who try these injections do so after treatments like physical therapy, exercise, and injections with steroids don’t give them enough symptom relief.
HA injections are FDA approved for use in the knee only; however, some physicians will also use them in other joints with OA, such as the hip or ankle. For some patients, these injections provide pain relief by providing some cushioning in the knee. However, the relief does not last long-term and some, but not all, studies suggest that any relief a patient experiences with these injections is the result of the placebo effect, in which the patient feels relief only because he or she expects the treatment to work.
Individuals typically receive a series of three to five shots one week apart over three to five weeks. On average, it takes about five weeks to experience the full benefits of HA injection. In contrast, relief from corticosteroid injections occurs within days, though this relief diminishes significantly after about a month or two.
The theory behind these injections is that because people with OA have a lower than normal amount of HA in their joints, adding HA to the joint will improve symptoms by helping to cushion the joint. The injection seems to work by temporarily restoring the thickness of the joint fluid, allowing better joint lubrication and perhaps directly affecting pain receptors. Research shows that HA may also interfere with prostaglandins and cytokines, naturally occurring compounds that promote inflammation. Still other research has shown that HA may actually help encourage the joint to make new cartilage since hyaluronic acid is a major building block of cartilage.
Some studies have shown that HA injections can reduce pain for up to six months, but others have shown more limited results, with 30 to 40 percent of those receiving the injections showing no improvement. A recent study, found that there were certain characteristics that make a person less likely to show improvement with HA injections, including obesity, severe arthritis, being older than 65, and/or having HA or corticosteroid shots in the past.
Notably, the American Academy of Orthopedic Surgeons (AAOS) no longer recommends HA injections for knee OA because it says that there isn’t enough evidence the therapy provides “clinically important improvement.”
Common brand names/types of HA injections include:
· Supartz® FX
ACR Recommendation for HA Injections:
· For patients with OA of the knee, ACR has no recommendation regarding HA injections because of the lack of data from randomized clinical trials on either benefit or safety at the time of publication.
· For patients with OA of the hip, no recommendations were made for the use of hyaluronic acid injections because of the lack of data from randomized clinical trials on either benefit or safety at the time of publication.
· For patients with OA of the hand, ACR recommends not using either intraarticular corticosteroids or HA injections and, furthermore, provided no recommendation on the choice between corticosteroids and hyaluronates, if a provider decides to give an injection.
Effects of HA Injections?
Side effects from HA injections are generally mild. The most common side effects with HA injections are difficulty with moving**,** muscle pain, warmth at the injection site, stiffness and/or joint pain. You may have temporary pain or swelling in the knee joint after injection. Call your doctor if the pain or swelling persists or becomes worse. Less common but more serious side effects include:
· Discoloration of the skin
· Feeling of pressure
· Redness or inflammation
· Itching or rash
How to Prevent or Reduce Side Effects
Let your doctor know if you have unpleasant side effects like swelling or increased pain in the injected joint(s), or any listed above. Don’t try to treat severe side effects on your own. Though rare, some people are allergic to HA. Call your doctor immediately if you notice any signs of an allergic reaction including difficulty breathing or swallowing, hives, severe itching or redness/inflammation around the injection site.
By David Borenstein MD, past president American College Rheumatology & CH Weaver MD Medical Editor