Glucosamine and chondroitin sulfate supplements are very popular treatments for OA. Unfortunately, robust scientific evidence that demonstrates their effectiveness in treating this condition is lacking.
Glycosaminoglycans are the building blocks for cartilage. Glucosamine is a precursor to a glycosaminoglycan; chondroitin sulfate is the most common glycosaminoglycan found in human cartilage. The rationale for taking these supplements is the belief that they might help to build new cartilage, repair OA-related damage, or slow the progression of new damage. To date, these purported effects have consisted largely of hopeful speculation, though this speculation has prompted many scientific trials of these supplements.
Unfortunately, the studies performed so far have been of poor quality. Most included only a small number of patients and had a very short duration. Furthermore, many of these studies were underwritten by manufacturers of the supplements (a conflict of interest). Perhaps not surprisingly, the manufacturer-sponsored studies seemed to come up with rosier conclusions than larger, more recent, and more objective studies. As a result, the earlier studies are of limited value when we try to judge the effectiveness of a treatment for a disease that affects millions of people and lasts for many years.
In response to the popularity of these supplements and the lack of good science supporting their use, a branch of the National Institutes of Health undertook a study to see how these dietary supplements affected OA. This study, which was called the Glucosamine/Chondroitin Arthritis Intervention Trial (GAIT), was the first large-scale, multicenter clinical trial in the United States to test the effects of glucosamine hydrochloride (glucosamine) and sodium chondroitin sulfate (chondroitin sulfate) for treatment of knee OA. The study investigated whether glucosamine and chondroitin sulfate, when used either separately or in combination, reduced pain in patients with knee OA. It reached the following conclusion:
Glucosamine and chondroitin sulfate alone or in combination did not reduce pain [emphasis added] effectively in the overall group of patients with osteoarthritis of the knee. Exploratory analyses suggest that the combination of glucosamine and chondroitin sulfate may [emphasis added] be effective in the subgroup of patients with moderate-to-severe knee pain.
As discouraging as those results were, many people remain motivated to try these supplements. Patients believe that these supplements are relatively inexpensive and safe. Moreover, many are frustrated with a lack of improvement of their pain from their prescription medications and want to avoid knee replacement surgery.
If you think you might benefit from these supplements or have questions about their risks and benefits, it's worthwhile to discuss this topic with your doctor.