The articular cartilage is the cartilage covering the diarthrodial joints. It is formed of chondrocytes within an extracellular matrix. This is formed of water, collagen, proteoglycan and glycoprotein. During intrauterine development future long bone is mainly cartilagenous and undergoes endochondral ossification. Later postnatally secondary ossification occurs at the cartilagenous extremities. This advancement of secondary ossification progressively defines a layer of cartilage at the joint surface. Its thickness depends on the distance at which secondary ossification stops.