Both glucosamine and chondroitin sulfate are sold as dietary or nutritional supplements. They are extracted from animal tissue: glucosamine from crab, lobster or shrimp shells; and chondroitin sulfate from animal cartilage, such as tracheas or shark cartilage.

What do they do?
Past studies show that some people with mild to moderate osteoarthritis (OA) taking either glucosamine or chondroitin sulfate reported pain relief at a level similar to that of nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen. Some research indicates that the supplements might also slow cartilage damage in people with OA. Definitive results about the effects of these supplements are expected from an in-depth clinical study currently being conducted by the National Institutes of Health.