What is cartilage?

Joints need cartilage to function properly. Up to eight times more slippery than ice, and with the ability to soak up and push out water as easily as a sponge, cartilage is perfectly designed to permit seamless motion between bones, while at the same time providing ideal shock-absorbing capacity. In the world of joints, cartilage is a true superhero. Scientists have put men on the moon, eradicated polio, made flying an everyday event, and decoded DNA, but they haven't yet been able to create a substance that is better suited for joints than the body's own healthy cartilage.

Cartilage is made of collagen, proteoglycans (core proteins that are attached to carbohydrate chains), chondrocytes (cells that make cartilage), and up to 80 percent water. When you are at rest and your joints are not bearing weight, cartilage stores synovial fluid and water within it. When a joint is loaded with a force, the fluid stored in the cartilage is redistributed to the joint. In other words, when you stand from a seated position, the weight you put on your knee pushes the synovial fluid and water out of the cartilage in your knee, much as it would push the water out of a wet sponge inside your knee. The fluid pushed into the joint space helps to cushion your weight and also nourishes the joint. It moves back into the cartilage when you sit down.

In addition to this sponge-like property, cartilage has another cushioning advantage -- it is filled with negatively charged chondroitin molecules. Negative particles resist touching each other with astounding atomic force. When the joint is made to bear weight, these chondroitin molecules are pushed together, but their negative charges resist. Pushing two negatively charged chondroitin molecules together is like trying to force two negatively charged magnets together. The closer they come to touching, the stronger they repel each other.

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, 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. Although cartilage is very strong, it can be damaged when a joint is injured.

Cartilage, a tough but slippery tissue, coats the ends of the joint bones. Sixty-five percent to 80% of cartilage tissue consists of water. The rest is made up of collagen, proteoglycans, and chondrocytes. The breakdown of cartilage contributes to the development of osteoarthritis. Normal cartilage can repair itself up to a point, even if a joint has been damaged. There is reason to believe that when the cause of the damage is removed and the joint is used normally, healing can occur.

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