How does the structure of the cartilage matrix contribute to joint function?
Normal cartilage is resilient, firm, and slippery because of the arrangement of collagen fibres and GAGs in the matrix. These two components bind together, forming a spongy network that combines the water-holding characteristics of the GAGs with the high tensile strength of collagen. When weight is applied to the joint, water is squeezed out of the matrix sponge and into the joint space. When the pressure is released, the GAGs pull water back into the matrix, absorbing as much as their binding with collagen will allow. This sponge-like action of the matrix has several effects: firstly, it is what gives cartilage its resiliency. Secondly, the water extruded from the matrix reduces friction and contributes to joint lubrication. Thirdly, and most importantly, the cycling of water from the matrix again carries nutrients to the chondrocytes and removes waste products from them. This is crucial to cartilage function, because unlike most tissues, cartilage has no internal blood vessels.
