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 localised, or may detach and fall into the joint space causing pain and joint instability.
The knee, mostly the femoral condyles are most commonly affected. The two femoral condyles make up for the rounded end of femur (thigh bone). 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. 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.
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.
Exact cause for osteochondritis dissecans remains unknown and certain factors such as trauma, fractures, sprains, or injury to the joint are considered to 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 and finally the bone fragment may break off. This may initiate the healing process however by this time, articular cartilage will be compressed, flattened, and a subchondral cyst will be developed. All these changes in addition to increased joint pressure cause failure of healing of the joint.
The appearance of osteochondritis dissecans in several family members may indicate that the condition is inherited.
Patients with osteochondritis dissecans usually have joint pain, swelling, stiffness, decreased range of motion, and joint popping or locking. Pain usually increases after activity.
Your doctor will probably order an X-ray of both the right and left knee to see the 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.
Your physician may recommend various treatments depending on the reports of diagnostic scans, age, severity, stability of the cartilage and other factors. Goals of treatment are to relieve the symptoms and stop or impede the progression of degeneration of the joint. Conservative treatment approaches such as wait & watch approach, pain medications, and immobilisation for 1-2 weeks are recommended if the condition is diagnosed at early stages and if the severity is mild. However surgery is required if the condition is diagnosed at advanced stage or if the condition is severe.
Surgical correction of osteochondritis dissecans can be done by open technique or arthroscopic techniques. Some of the surgical procedures include drilling, bone grafting, open reduction internal fixation, osteochondral grafting, or autologous chondrocyte implantation (ACI).