The term degenerative joint disease describes a wearing out of the joint over a period of many years. Injury to a joint, such as a bad sprain or fracture, can damage the articular cartilage. Excessive pressure on the cartilage surface of a joint can also damage the cartilage. If you look at the surface it may not appear to be any different since injury to the cartilage doesn’t appear until months later. Sometimes the cartilage surface is severely damaged, ripping cartilage pieces from the bone that must be removed from the joint surgically so they don’t cause the joint to catch and cause additional cartilage damage.
Torn or fractured pieces of cartilage do not normally grow back. The defects are filled with scar tissue that is not nearly as good a material for covering joint surfaces as the cartilage it replaces.
An elbow joint injury can alter how the joint works even if it does not injure the articular cartilage directly. When an injury changes the way the elbow joint moves, forces on the articular cartilage surfaces may be increased. Like any mechanical device, if the mechanism is out of balance it wears out faster.
Over many years an imbalance in the joint mechanics can lead to damage. When the joint becomes unable to compensate for the increasing damage, it begins to hurt.