The condition known as osteochondritis dissecans or OCD is an acquired injury from repetitive microtrauma. A lack of blood supply to the damaged area causes separation of the first two layers of the knee joint: the cartilage that lines the joint (articular cartilage) and the subchondral bone (bone just under the cartilage).
The end-result is a hole (referred to as a “lesion” or “defect”) in the knee joint cartilage that goes down to the bone. The defect is on the bottom of the femur (thigh bone) where the femur comes in contact with the tibia (lower leg bone). Instability of the articular cartilage causes pain, swelling, and loss of knee motion and knee function. Left untreated, uneven contact of the joint eventually causes further degeneration of the joint and arthritis.
Many studies have shown that the prognosis for OCD is poor without surgery. Young patients with very small, stable lesions have the best chance for healing with conservative (nonoperative) treatment. But usually, because the area affected is the weight-bearing surface of the knee, compressive forces from standing and walking just further erode the damage already present.
The joint no longer lines up evenly on both sides. An uneven wear pattern develops and significant osteoarthritis is the final outcome. Studies have also shown that patients with untreated OCD can expect degenerative osteoarthritis a full 10 years before someone who doesn’t have an OCD defect.
The bone has some potential for regeneration but self-healing is limited. That’s why surgery to aid the process seems to have the best results. The goal of surgery is to restore the joint surface to as normal as possible (anatomically). There are a variety of surgical techniques available to treat this problem. Our publication A Patient’s Guide to Osteochondritis Dissecans of the Knee provides more information on the various types of treatment. You may find this document informative and helpful in understanding your condition.