Dr. Florent Richy, MSc, an epidemiologist at the University of Liege, Belgium, evaluated 15 studies on osteoarthritis (OA) of the knee. The combined studies represented 1,775 volunteers, 1,020 taking glucosamine and 755 taking chondroitin. In the studies, it took about two weeks of supplementation for participants to begin experiencing pain relief and greater joint flexibility. It appeared that taking at least 1,500 mg per day of glucosamine for at least three years was most effective in slowing the degenerative process. In most of the studies, the dosage range for chondroitin was 800 mg to 1,200 mg per day, usually administered in divided doses. Dr. Richy noted the best dosage for chondroitin has not been determined.
Glucosamine and chondroitin are components of joint cartilage. Cartilage acts as a joint cushion, and glucosamine stimulates the formation and repair of cartilage, while chondroitin helps to draw fluid into cartilage, making it more elastic. OA is most commonly a wear-and-tear disease that involves degeneration of joint cartilage and formation of bony spurs within the joints. The more frequently the following symptoms occur, the more likely it is that OA may be developing: stiffness of the joints upon awakening, swollen joints, joint pain, popping or grinding sounds in joints, and/or a warm sensation in one or more joints.
The risk of developing OA of the knee increases steadily with age. Contributing factors include genetics, joint injury, mechanical stress, and obesity. Six percent of U.S. adults age 30 and over have OA of the knee, and the incidence increases to 30% among those between 65 and 74. Before age 50, more men than women are affected by OA of the knee, but after age 50 the condition is more prevalent in women, who generally begin suffering shortly after menopause. Tests have shown that unlike aspirin and non-steroidal anti-inflammatory drugs used in arthritis, glucosamine and chondroitin have few side effects.