Glucosamine and chondroitin sulfate are naturally occurring substances found in normal joint tissue. Glucosamine is believed to play a role in cartilage formation and repair, and chondroitin sulfate gives cartilage its elasticity. Osteoarthritis, also known as degenerative joint disease, is the result of hardening and destruction of the cartilage in the joints causing pain, deformity and limitation of movement. The most common cause of osteoarthritis is the cumulative effects of years of joint use compounded by the lessening ability to restore joint cartilage as we age.