Anatomy of the Knee Joint
Two femoral condyles make up the rounded end of the femur (thighbone). Each knee has two femoral condyles, the medial femoral condyle on the inside of the knee and the lateral femoral condyle on the outside of the knee.
What is Osteochondritis Dissecans?
Osteochondritis dissecans is a joint condition in which a piece of cartilage, along with a thin layer of the bone separates from the end of the bone because of inadequate blood supply. The separated fragments are sometimes called “joint mice”. These fragments may be localized or may detach and fall into the joint space, causing pain and joint instability. Osteochondritis dissecans occurs within the lateral aspect of the medial femoral condyle. The condition can also occur in other joints, including your elbows, ankles, shoulders, and hips.
Incidence of Osteochondritis Dissecans
Osteochondritis dissecans is more common among boys and young men between 10 and 20 years who actively take part in sports. Athletes participating in sports such as gymnastics and baseball may develop osteochondritis dissecans.
Causes of Osteochondritis Dissecans
The exact cause for osteochondritis dissecans remains unknown and certain factors such as trauma, fractures, sprains or injury to the joint can increase the risk of developing the condition. Osteochondritis dissecans may be caused by restricted blood supply to the end of the affected bone that usually occurs in conjunction with repetitive trauma. Following the injury or trauma, the bones in the area may be deprived of blood flow, leading to necrosis; finally, the bone fragment may break off. This may initiate the healing process; however, by this time, the articular cartilage will be compressed, flattened and a subchondral cyst may develop. All these changes, in addition to increased joint pressure, cause failure of the healing of the joint.
The appearance of osteochondritis dissecans in several family members may indicate that the condition is inherited.
Symptoms of Osteochondritis Dissecans
Osteochondritis dissecans usually causes joint pain, swelling, stiffness, decreased range of motion, and joint popping or locking. Pain usually increases after activity.
Diagnosis of Osteochondritis Dissecans
Your doctor will probably order an X-ray of both the right and left knee to determine any abnormality in the joint space and to compare them. You may also have a CT or MRI scan that is useful in determining the location of loose fragments within the joint.
Treatment of Osteochondritis Dissecans
Your physician may recommend various treatments depending on the reports of diagnostic scans, age, severity, stability of the cartilage and other factors. The goals of treatment are to relieve the symptoms and stop or impede the progression of joint degeneration.
Conservative treatment approaches such as the wait-and-watch approach, pain medications and immobilization for 1-2 weeks are recommended if the condition is diagnosed at the early stages and if the condition is mild. However, surgery is required if the condition is diagnosed at an advanced stage or is severe.
Surgical correction of osteochondritis dissecans can be performed using the open or arthroscopic technique. Some of the surgical procedures include:
- Drilling: In this method, multiple small holes are drilled into the bone to allow the growth of new blood vessels in the defected area. This promotes blood flow into the defective area; thereby, initiating the healing response and formation of new cartilage cells inside the lesion.
- Open reduction internal fixation: Open surgery is performed in cases where the defected area is difficult to reach with an arthroscope. Hence, an open incision may be required. In this procedure, an incision is made in front of the joint to allow your surgeon to view the joint and remove the loose bodies. Internal fixation involves fixing the fragments using internal fixators such as metal screws, pins, and wires.
- Bone grafting: It helps to fill the gap after the removal of the dead or necrotic bone. In this procedure, bone graft is placed on the damaged site. This procedure may be performed to repair the damaged area or replace the missing bone. Autograft (harvested from the same individual) or allograft (taken from the bone bank) may be required to help in the growth of a new bone.
- Osteochondral grafting: The procedure involves the transfer of healthy cartilage plugs from a non-weight-bearing area of the joint to the damaged area of the joint in a mosaic pattern. It allows the newly implanted bone and cartilage to grow in the defected area. Grafts may be taken from your own body (autograft), or from a donor or bone bank (allograft).
- Autologous chondrocyte implantation (ACI): In this procedure, healthy cartilage cells are harvested from your non-weight-bearing joint and cultured in the laboratory. The cultured cartilage tissue patch will be implanted into the defected area to promote the growth of new cartilage.