Osteochondritis Dissecans (OCD) is a condition that affects the articular cartilage and the subchondral bone of the knee. The lesion usually occurs in the knee on the lateral and posterior aspect of the medial femoral condyle (70% of lesions are in the posterolateral aspect of the knee).
The Distribution of OCD Lesion around the knee are as follows:
- Medial Femoral Condyle- 85%
- Lateral Femoral Condyle- 13%
- Patella- 1%
- Trochlea- 1%
The chances of the lesion occurring at the lateral condyle and patellar aspect of the knee is rare. Lateral condylar and patellar lesions will have a bad prognosis.
The mechanism and causes of injury for OCD lesions may be multifactorial; however, it is usually cause by repetitive overloading, causing fragmentation and separation of bony fragments. It can occur in juveniles with an open epiphysis usually during the ages of 10-15 years—the prognosis is usually very good. It can also occur in adults, with a less favorable prognosis.
Osteochondritis Dissecans of the knee are classified into four stages:
- Depressed OCD
- Intact cartilage
- Small area of compressed subchondral bone
- Partially Detached Fragment
- Completely Detached but Non-displaced
- The most common type
- Completely Detached and Displaced
- Displaced fragment can be a loose body
Symptoms include: activity related vague pain, poorly localized tenderness, effusion, and swelling and stiffness with or without mechanical symptoms (mechanical symptoms indicate an advanced problem).
The Wilson’s Test is a test used to detect the presence of Osteochondritis dissecans of the knee. During the test, you will ask the patient to sit on a table with their legs dangling over the edge—the patient’s knee should be flexed at a 90° angle. Then, you will grasp the patient’s leg and internally rotate the tibia. Instruct the patient to extend the leg until pain is felt. The test is positive when the patient reports pain in the knee about 30° from full extension. When rotating the leg back in its normal position, the pain disappears. Internal rotation causes impingement of the tibial eminence on the OCD lesion of the medial femoral condyle which causes the pain. External rotation moves the eminence away from the lesion, which relieves the pain.
As for imaging:
- X-rays
- Weight-bearing AP and Lateral view radiographs
- Tunnel View (intercondylar notch view)
- MRI
- Check the size of the lesion, signal intensity surrounding the lesion, and any presence of loose bodies.
The prognosis depends on age, location, and MRI findings. The younger the patient, the better the prognosis will be. Lesions in the lateral femoral condyle and patella will have a worse prognosis. Synovial fluid appearing behind the lesion on an MRI correlates with a worse prognosis. A fluid signal on an MRI behind the lesion indicates that the fragment is unstable and is less likely to heal.
Nonoperative treatment is preferred for stable lesions in children with open physes. The majority will heal as long as the physes is open (good prognosis). Nonoperative treatment consists of observation, limitation of activity, crutches, trial of non-weight bearing for six weeks and a close follow-up.
Operative treatment is indicated if the fragment is detached, unstable, or loose in patients where the physes has already closed, is near closing, or if there is failure of the non-operative treatment. Surgical treatment usually includes an arthroscopy as well as removal of the loose fragment, fixation of the unstable lesion, or microfractures, which is drilling of the lesion. Arthroscopic drilling of the subchondral bone is done in children who approach skeletal maturity. Drilling of the lesion has a high success rate, especially if the lesion is stable.
