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Cartilage is a type of hard, 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, including the spine and the rib cage. 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, meshlike 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.