New England Journal of Medicine (2006; 354(8): 795-808) looked at supplementation with glucosamine and chondroitan and its effect on knee pain from osteoarthritis. The 1,583 subjects were part of the Glucosamine/chondroitan Arthritis Intervention Trial (GAIT), a double-blind, placebo-controlled study. Participants were randomly selected to receive celecoxib (Celebrex), glucosamine hydrochloride, chondroitan sulfate, a combination of chondroitan sulfate and glucosamine, or a placebo for a period of 24 weeks.

Successful treatment was defined as a 20% decrease in pain between the beginning of the study and the 24th week. The combination of glucosamine and chondroitan was slightly better than placebo. For the overall group, 60.1% of the placebo group having a 20% improvement and 66.6% of the group taking the combination of supplements (compared to 70.1% for celecoxib). The glucosamine/chondroitan combination performed very well for patients with moderate to severe knee pain, with 79.2% experiencing improvement.