In osteoarthritis , cartilage in a joint (e.g., hand, hip, knee, or spine joint) wears away, leading to pain, swelling, and loss of motion. Pain relief medications can help manage symptoms of osteoarthritis, but since they have been associated with adverse effects, more and more people are using the dietary supplements glucosamine and chondroitin sulfate . Some studies have suggested that these supplements are beneficial, but the scientific quality of the research has been questionable.

In a new study in the February 23, 2006 issue of the New England Journal of Medicine , researchers found that glucosamine, chondroitin sulfate, or the combination of the two was no more effective than a placebo in reducing pain in people with osteoarthritis of the knee. Most of the people in the study had relatively mild pain, but the supplements may have been beneficial in a subgroup of participants who reported moderate to severe pain.

About the Study

This study included 1,583 people with painful knee osteoarthritis. The researchers randomly assigned the participants to receive one of the following:

  • 1,500 milligrams (mg) of glucosamine daily
  • 1,200 mg chondroitin sulfate daily
  • 1,500 mg glucosamine plus 1,200 mg chondroitin sulfate daily
  • 200 milligrams of celecoxib (an approved medication for treating osteoarthritis) daily
  • Placebo

The researchers tracked the number of participants in each group who experienced a 20% decrease in knee pain after 24 weeks of the study.

Overall, glucosamine, chondroitin sulfate, or the combination of the two were no more effective than the placebo in decreasing pain. As expected, significantly more (10% more) participants in the celecoxib group than in the placebo group experienced a 20% decrease in knee pain during the study. Among the participants who reported moderate to severe pain at the start of the study, 79% of those in the glucosamine plus chondroitin sulfate group experienced a 20% decrease in pain, compared with 54% in the placebo group.

These findings are limited because 60% of the participants in the placebo group experienced a 20% decrease in pain. This “placebo effect” may have masked other findings.

How Does This Affect You?

This study questions whether taking glucosamine and chondroitin sulfate is effective in managing symptoms of knee osteoarthritis. But it also suggests that the supplement combination may be effective in a certain group of knee osteoarthritis patients—those experiencing moderate to severe pain. If you have osteoarthritis and are interested in taking glucosamine and chondroitin sulfate, talk with your physician. He or she can ensure you are taking safe dosages and can recommend other strategies to help manage your symptoms.

Randomized controlled trials involving dietary supplements are important because supplements are not stringently regulated by the Food and Drug Administration (FDA) like over-the-counter and prescription medications are. With dietary supplements, the manufacturer—not the government—is responsible for determining that the supplement is safe and that claims about effectiveness are substantiated. In this trial all supplements were chemically tested for their content and potency, but non-study purchasers of chondroitin or glucosamine cannot be equally assured that their supplements contain the ingredients specified. However, as this trial demonstrates, supplements, even when fully tested for potency, may not be effective as their manufacturers would have you believe. Unfortunately further studies will still be needed. Stay tuned.