The articular cartilage is the lining of the joint on each of the bones articulating with each other. The type of cartilage lining is defined as hyaline cartilage and consists of water, collagen, complex proteins (proteoglycans) and cartilage cells (chondrocytes). Cartilage decreases friction and distributes loads. Cartilage has a very limited ability to heal and defects tend to worsen over time. Injuries can cause cartilage damage but aging also results in gradual degeneration. In general any force exceeding 24 MPa will cause damage to the articular cartilage.