These pieces do not heal back and usually must be removed from the joint surgically. If not, they may float around in the joint causing the joint to catch and be painful. These fragments of cartilage may also do more damage to the joint surface. The areas where these pieces of cartilage are ripped from do not normally grow back. Unlike bone, the holes in the surface are not simply replaced by the cartilage tissue around the hole. Instead the defects are filled with scar tissue. The scar tissue that forms is not nearly as good a material for covering joint surfaces as the cartilage it replaces. It just can't support weight bearing like true articular cartilage.
An injury to a joint, even if it does not injure the articular cartilage directly, can alter how the joint works. This is true for a fracture where the bone fragments heal slightly different from the way they were before the break occured. It is also true that when ligaments are damaged it leads to instability in the joint. When an injury results in a change in the way the joint moves, the injury may increase the forces on the articular cartilage. This is very similar to any mechanical device or machinery. If the mechanism is out of balance, it wears out faster.
Over many years this imbalance in the joint mechanics can lead to damage to the articular surface. Since articular cartilage cannot heal itself very well, the damage adds up. Finally, the joint is no longer able to compensate for the increasing damage and it begins to hurt. The damage is occurring well before the pain begins.
Degenerative arthritis may come from differences in how each of us is put together based on our genes; a condition best described as osteoarthritis. Or degenerative arthritis may come years after an injury has occured that leads to slow damage to the joint surfaces; a condition probably best described as post- traumatic arthritis. Either way the joint is worn out - and it hurts. |