Glucosamine is a natural compound that is found in healthy cartilage. In the past, some researchers thought glucosamine may actually slow progression of the disease, unlike other current medical treatments for OA. Many people take either acetaminophen (Tylenol) or nonsteroidal anti-inflammatory drugs, such as ibuprofen (Advil, Motrin) and naproxen (Aleve), for OA pain. In addition, some of these drugs can cause stomach upset, cramps, constipation, diarrhea, and in some cases, stomach ulcers and infertility. from:ebiochem.com

Glucosamine is often combined with chondroitin sulfate, a molecule naturally present in cartilage. Chondroitin gives cartilage elasticity and is believed to prevent the destruction of cartilage by enzymes. Glucosamine is sometimes combined with methylsulfonylmethane, or MSM, in nutritional supplements. Because glucosamine can help the everyday rebuilding of the connective tissues around your joints,  including your tendons, ligaments and cartilage. These tissues are continuously being formed and reformed during normal everyday activity. from:ebiochem.com

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable health care provider. Studies suggest that glucosamine is safe, and causes only minor side effects, such as stomach upset, heartburn, indigestion, gas, bloating, nauseau, and diarrhea. If these occur, try taking glucosamine with food. People with peptic ulcers should take glucosamine sulfate with food. from:ebiochem.com