Although our bodies generally use glucose to produce energy, the aminosugars found in glucosamine are incorporated into the structure of body tissue. Glucosamine is involved in the formation of cartilage, nails, tendons, skin, eyes, bones, ligaments, and heart valves. It also plays a role in the mucous secretions of the digestive, respiratory, and urinary tracts. Of particular interest is its role in cartilage. It separates bones so that they do not grind together, causing stiffness and pain.
Cartilage also serves as a shock absorber.
Briefly put, cartilage protects our bones from the wear and tear of movement. One way to think of cartilage is as a super sponge. As the joint rests again, it again soaks up water. This spongelike effect of cartilage makes it a shock absorber, buffering our bones and body from the wear and tear of making thousands of movements per day. Thus, when two bones do meet, the cartilage at the ends of each bone allows them to slide off each other, adding to the buffering effect.