Glucosamine is a basic building block of animal and human cartilage (the tissue that lines, cushions, and lubricates skeletal joints). Cartilage is a complex matrix of collagen fibers interwoven with proteoglycan molecules. Proteoglycans are large and complex macromolecules comprised of long chains of polymerized amino-sugars (a principle one being glucosamine). These provide a framework for the collagen matrix and hold water to give the cartilage flexibility, resiliency, and resistance to compression.
Because of its important role in regulating cartilage formation, glucosamine has been used clinically in the treatment of osteoarthritis.