Chronic Disease

Injection of hyaluronic acid, a natural joint lubricant, appears effective in reducing pain from wear and tear on the knee

Some patients with pain from osteoarthritis of the knee may get better pain relief from an injection of hyaluronic acid, a natural lubricant of the joint, than from painkillers or steroids, according to a review of studies. Injection of hyaluronic acid into the knee, a treatment termed intra-articular hyaluronic acid (IAHA), has been used increasingly by clinicians because of IAHA's claimed prolonged effect in reducing symptoms from osteoarthritis.

In this study, researchers examined the results of 54 clinical trials, published between 1983 and 2009, which compared IAHA with placebo. They found that IAHA's pooled effect size for pain-relief (expressed as a standardized mean difference) was 0.31 at week 4 after treatment, reached its peak effect at week 8 (0.46), and remained detectable at 24 weeks (0.21). An effect size above 0.20 is considered clinically relevant for patients with chronic pain conditions like knee osteoarthritis. These results for relief of osteoarthritis pain were better than the results published for analgesics, which ranged from 0.13 for acetaminophen and 0.29 for nonspecific anti-inflammatory drugs to 0.44 for COX-2 inhibitors.

The pooled data for those studies measuring improvement in joint function and joint stiffness indicated no effect of IAHA after excluding low-quality trials. Based on these findings, the researchers suggest that IAHA may be useful for knee pain in some patients, or in combination with other treatments. The study was funded in part by the Agency for Healthcare Research and Quality (T32 HS00060 and HS18574).

More details are in "Therapeutic trajectory following intra-articular hyaluronic acid injection in knee osteoarthritis—meta-analysis," by Raveendhara R. Bannuru, M.D., Nikola S. Natov, M.D., Usha R. Dasi, M.D., and others in Osteoarthritis and Cartilage 19(6), pp. 611-619, 2011.

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