THE QUESTION Seeking relief from the pain, stiffness and diminished function caused by osteoarthritis in their knees, people often take the dietary supplements glucosamine and chondroitin. Is that likely to help?

THIS STUDY analyzed data on 1,625 adults who had osteoarthritis in at least one knee and had X-rays taken annually to assess damage to the affected joint. At the start of the study, none of the participants had taken glucosamine or chondroitin, singly or together, but during the next three years, 18 percent of them started taking the supplements at least four days a week.

Nearly everyone took them in combination. The results from X-rays and standardized scales rating pain, stiffness and function showed essentially no difference between those taking and not taking the supplements. Glucosamine/chondroitin neither relieved symptoms nor retarded progression of the disease.

WHO MAY BE AFFECTED? People with knee osteoarthritis, which develops when a lack of cartilage between the bones of the joint causes them to rub together, resulting in pain and swelling that restricts movement.

Most often, gradual wear and tear on the joint causes the cartilage to thin, not providing the usual shock absorption and protection. Osteoarthritis is a progressive disease, meaning it gets worse over time.

(Bigstock)

CAVEATS Data on use of glucosamine/chondroitin and on symptoms came from the participants’ responses on periodic surveys. Supplements may have varied in dosage and composition. The pharmaceutical companies Merck, Novartis, Glaxo­SmithKline and Pfizer helped fund the study.

FIND THIS STUDY Nov. 4 online issue of Arthritis and Rheumatology (click on “All Issues”)

LEARN MORE ABOUT osteoarthritis at www.arthritis.org and niams.nih.gov.

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.