Glucosamine is an amino sugar normally formed in humans from glucose. Glucosamine is one of the biological chemicals that forms all the major cushioning ingredients of the joint fluids and surrounding tissues. It helps make the fluid thick and elastic. In certain cases of trauma to the tissues, the amount of Glucosamine normally produced by the body is insufficient. If the joint cushioning is lost or becomes thin, the bones and cartilage scrape together causing pain and problems with joint movement and flexibility. Pressure may also be put on the nerves causing damage and loss of nerve function.