Cartilage is a type of firm, thick, slippery tissue that coats the ends of bones where they meet with other bones to form a joint. Cartilage lines the joint space between bones throughout the body, and it acts as a protective cushion between bones to absorb the stress applied to joints during movement.

Cartilage is made up of protein strands called collagen that form a tough, mesh-like framework. The mesh is filled with substances that hold water, much like a sponge. When weight is placed on cartilage, water is squeezed out of the mesh. When weight is taken off, the water returns. Cartilage does not contain blood vessels or nerves. Although cartilage is very strong, it can be damaged when a joint is injured.