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The extracellular matrix of cartilage is a complex maze of proteoglycans and proteins. Depending on the type of cartilage, either collagen or elastic fibers are interwoven in an interfibrillar substance of large proteoglycan complexes, mainly chondroitin sulfate. The unique molecular structure of the proteoglycan maze attracts water molecules within the complex intermolecular spaces. Large amounts of water (the most abundant substance of cartilage) occupy these spaces. When the cartilage is compressed, the water moves. This movement of water within the cartilage helps this tissue absorb jarring movements. Furthermore, cartilage is functionally important in joint lubrication by means of various “weeping” movements of water onto articular surfaces. The water is also important in establishing diffusional channels in the tissue to provide for the nourishment of its cells, as cartilage receives no direct blood supply. Instead, materials must diffuse between the surrounding tissue and cartilage cells.