Osteochondritis dissecans is a lesion of subchondral bone that may resolve spontaneously. Progressive lesions may involve the overlying articular cartilage. These lesions are most common about the knee, usually involving the medial condyle. Patellar lesions usually occur later than those of the condyles.
The cause is multifactorial with trauma, vascular insufficiency, and genetics being factors. OCD lesions are associated with lateral tibial torsion, genu varum and valgum, and meniscal lesions.
Juvenile OCD occurs in children with an average age of onset between 11 and 14 years. Boys are more commonly affected. Symptoms include pain, a mild effusion, or later mechanical symptoms. Because most lesions involve the posterolateral part of the medial femoral condyle, they are best shown by a notch view. Classify lesions based on degree of displacement. Sometimes the displacement can only be appreciated on MRI or arthroscopy.
Irregular ossification of the lateral condyle may be a normal variation of ossification and not osteochondirits dissecans. These variations are often bilateral and found incidently when radiographs of the knee are made. They do not cause pain or effusion, and are nontender.
Small lesions in children or early adolescence often resolve without treatment. Larger lesions, older age, and a weight-bearing location are more likely to displace and cause joint damage and eventual osteoarthritis. Aggressive treatment of these lesions is appropriate.
Management depends upon the site, size, patient’s age, and classification of the lesion.
Type 1 and 2 lesions Manage with activity modification, isometric exercises, and a knee immobilizer. Manage based on symptoms rather than on radiographic appearance. Radiographic healing takes many months.
Type 3 lesions Manage by drilling and stabilizing with K wires or absorbable pins.
Type 4 lesions Manage small lesions by excision. Replace large lesions or those involving the weight-bearing areas and fix internally if adequate subchondral bone exists on the fragment.
Up to 90% of small lesions in juvenile OCD may heal spontaneously. Lesions with an onset later, especially large lesions in weight-bearing regions of the knee, require aggressive treatment. Management is not always successful, and osteoarthritis may occur in adult life.