Glucosamine and chondroitin are normal constituents and important structural components of joint cartilage. Several smaller studies had suggested they may be of value to people with knee pain from osteoarthritis. A very large multicenter study that involved over 1,500 patients evaluating their efficacy and safety was just published in the New England Journal of Medicine. For patients with moderate-to-severe pain, the combination of glucosamine and chondroitin sulfate was effective at reducing pain without side effects.