Our 16-year old son has developed OCD of the left knee. He’s spent six months trying to rehab it but needs surgery anyway. The surgeon says to expect six to eight months’ time to heal AFTER the operation. What takes so long? I thought in a young person everything heals much faster.

Osteochondritis dissecans (OCD) is a problem that affects the knee, mostly at the end of the big bone of the thigh (the femur). A joint surface damaged by OCD doesn’t heal naturally.

The problem occurs where the cartilage of the knee attaches to the bone underneath. The area of bone just under the cartilage surface is injured, leading to damage to the blood vessels of the bone. Without blood flow, the area of damaged bone actually dies.

The lesions usually occur in the part of the joint that holds most of the body’s weight. This means that the problem area is under constant stress and doesn’t get time to heal. In the child who is still growing, the problem is much more likely to heal itself. In the adult, the bones are not growing and take longer to heal. Many 16-year old boys have completed their growth and respond more like an adult to this problem.

Surgery to repair the problem can be successful but healing does take time. If a bone graft is used, healing begins inside the bone. Bone cells begin on the inside and grow outward toward the torn cartilage. Bone graft has the advantage of stimulating blood flow to the area. Pins used to hold the torn fragment in place don’t bring new blood to the area.

Plugs of bone graft used to repair OCD can heal as quickly as three months. If the surgeon is planning to use hardware such as pins, the healing process can take longer.