Cartilage is a flexible connective tissue which can rapidly grow and which is specialized to absorb and resist compression. The perichondrium, a vascularized layer, surrounds the tissue which does not contain any blood vessels of its own. Therefore nutrients and waste material have to be able to diffuse through the cartilage tissue. A thin layer of smooth hyaline cartilage (the so called articular cartilage) covering the joint surfaces of the bone, does not have any perichondrium though. Articular cartilage is protected by synovial fluid, a nutritive and lubricating medium.