OSTEOCHONDRITIS DISSECANS

QUESTION |  I HAVE A 16 YEAR OLD MALE ATHLETE WHO PRESENTED WITH A VAGUE HISTORY OF KNEE PAIN WHEN RUNNING – X RAY SHOWED AN OCD LESION. WHAT IS THE BEST TREATMENT FOR HIM?

ANSWER | Osteochondritis dissecans of the knee predominantly affects teenagers and people in their early 20’s. Many of these patients are involved in running sports and this condition can have a dramatic impact on them. OCD can lead to pain, swelling, mechanical symptoms and is the most common cause of a loose body in the knee in adolescents. Clinical findings can be subtle so diagnosis requires a high index of suspicion with limited range of motion sometimes the only clinical sign. Most patients provide a history of trauma as their reason for their presentation but this is usually minor and probably not relevant. In some patients the affected femoral condyle is tender to palpation. Some patients walk with the leg externally rotated in order to avoid contact of the lesion (on the medial femoral condyle) with the tibial plateau but most do not.

The diagnosis is made on xray but MRI has a key role in determining the stability of the lesion. Conservative management is the mainstay of treatment for stable lesions. The majority of patients respond to conservative treatment but those with unstable lesions require arthroscopic (or open) management. Unfortunately the affected knee may progress to degenerative arthritis while the patient is still young.

The etiology of OCD remains unknown despite several theories which have been proposed. These include genetics (family history), repetitive micro-trauma, growth disorders, and ischaemia. The characteristic finding of OCD is a focal area of subchondral bone that undergoes necrosis. The true incidence is unknown but is higher in males than females. OCD can involve other joints including the shoulder, elbow, hip, and ankle, but the knee is the most commonly affected. The natural history of OCD of the knee remains unclear and knowing which lesions will heal and which will not heal remains a challenge. High quality studies that report data separately for adults and children are rare and many of the publications dealing with OCD of the knee are only level IV evidence (case series).

Treatment is aimed at pain relief, improvement of knee function and prevention of arthritis. Nonsurgical treatment presents a challenge because it is difficult to predict which stable juvenile OCD lesions will heal. In the early stages arthroscopic surgery can be very effective but open surgery is still sometimes required.

OCD refers to a focal area of subchondral bone that undergoes necrosis. The overlying cartilage remains intact to variable degrees, receiving nourishment from the synovial fluid. As the necrotic bone is resorbed, the cartilage loses its supporting structure and the fragment can displace into the joint. There are two main types of OCD: the adult form, which occurs after the physis closes; and the juvenile form, which occurs in patients with an open epiphyseal plate (some people believe that the adult form is undiagnosed persistent juvenile OCD).

The knee is involved about 75 percent of the time. The lateral (mainly nonweight-bearing) part of the medial femoral condyle is the location in 85 percent of cases of OCD of the knee. OCD should be ruled out in the contralateral joint because 20 to 30 percent of cases are bilateral. Multiple lesions are rare but possible. Less frequent locations include the patella, femoral head, glenoid of the scapula, tibial plateau, head of the talus and vertebrae. Capitellar lesions of the humerus are common in adolescent baseball pitchers and gymnasts but while they look the same are probably a different disease process.