ABSTRACT
Hyaline (literally, 'glass-like') cartilage coats the articular surfaces of synovial joints. The structure of articular cartilage can be divided into layers as seen on histological examination. Collagen synthesis takes place in stages both within and outside the chondrocyte. Proteoglycans are responsible for most of the water content of cartilage and also provide compressive strength to cartilage. They are large hydrophilic molecules containing chains of glycosaminoglycans (GAG) (chondroitin sulphate, keratan sulphate) bound by covalent bonds to a linear core of protein. Cartilage typically has a high sodium and potassium ion content. The articular chondrocyte is derived from uncommitted mesenchymal stem cells (MSCs). The main functions of articular cartilage are joint lubrication and shock absorption. Articular cartilage is variably permeable to fluid, depending on whether it is loaded. As the articular cartilage of the joint slides under compression, fluid is exuded under and in front of the leading edge of the load, enhancing lubrication.
