Hyaline cartilage consists of a matrix that includes protein and sugar compounds (proteoglycans and glycosaminoglycans such as chondroitin sulfate, keratin sulfate, and hyaluronic acid) synthesized by chondrocytes (cartilage-forming cells); it's composed of the collagen fibers that give the cartilage structure. The glycosaminoglycan matrix of cartilage regenerates every one to three months, while the collagen structural elements are replaced even more slowly.