Osteoarthritis of the Knee: Hyaluronic Acid Joint Injections

In the U.S., almost 21 million adults are living with osteoarthritis. And one of the body's critical joints -- the knee -- is the most frequently affected. More than 30% of people over 50 have knee osteoarthritis. So do a whopping 80% of those over 65. In fact, about 100,000 people in the U.S. can't get from their bed to the bathroom because of osteoarthritis of the knee.

Getting hyaluronic acid joint injections is one treatment that may ease the pain and stiffness of osteoarthritis. Hyaluronic acid joint injections are quick and relatively painless. They've been on the market for more than a decade. But studies on effectiveness show mixed results.

Should you consider hyaluronic acid joint injections? There's no simple answer. Experts say it depends on your symptoms, the other treatments you've tried, and your own preference.

What Are Hyaluronic Acid Joint Injections?

Hyaluronan occurs naturally in the synovial fluid that surrounds the joints. Hyaluronan is a thick liquid that helps lubricate the joints, making them work more smoothly. It's also a shock absorber. It prevents your bones from bearing the full force of impact when you walk.

In people with osteoarthritis, the consistency of hyaluronan becomes thinner. As a result, it does a worse job of cushioning the bones. The idea behind hyaluronic acid joint injections is to replace some of the natural supply that's been lost.

The procedure is simple. Hyaluronic acid is injected directly into the cavity around the knee joint. A typical course of treatment is one injection a week for three to five weeks. While it has only been FDA-approved for people with osteoarthritis of the knee, it's sometimes tried in other joints as well.

Five different brands of hyaluronan are available:

• Euflexxa
• Hyalgan
• Orthovisc
• Supartz
• Synvisc

While the types do differ in some ways, H. Ralph Schumacher Jr., MD, a rheumatologist at the University of Pennsylvania Medical School and editor in chief of the Journal of Clinical Rheumatology, says that none has been shown to work better or worse than another.