Like everything else in our bodies, however, cartilage sooner or later wears out or is injured. For instance, a ring of cartilage with fluid in the middle is located between each of the backbones as a cushion for the spinal column. Sometimes, the ring of cartilage is torn and the fluid leaks out. This is called a ruptured disc and it is extremely painful. There are many reasons why cartilage injury occurs, but when it does, the injury progresses to loss of this protective shock absorber.
Bone rubs against bone, causing osteoarthritis.
OA, one of the oldest and most common types of arthritis, is a disease of the cartilage and leads to injury of the joint. It is not due simply to wear and tear or old age. Some physicians think of it as the end result of any injury to a joint. We have no explanation as to where it comes from or what causes it. Several theories about the cause of OA exist.