Osteochondritis dissecans (OD) is a focal aseptic necrosis of subchondral bone in which a bone-cartilage fragment detaches and becomes displaced in the joint space. School-aged children and adolescents are most commonly affected. OD occurs as a result of overuse or trauma, and 75% of cases affect the knee. Symptoms include pain and joint locking or catching. X-ray is the best initial test for suspected OD, but MRI is better able to detect early disease. First-line treatment includes reducing physical activity. Surgery is indicated if the bone-cartilage fragment is completely displaced and includes arthroscopic extraction, open fixation, and transplantation procedures.
The etiology is unknown. Proposed theories include mechanical stress and repetitive trauma.
- Most frequently affected joint: knee
- In early lesions, nonlocalized pain during physical activity in school-aged children or adolescents
- Gradual stiffness with joint locking or catching
- Antalgic gait with lateral rotation of the ipsilateral foot
- Pain on palpation of the femoral condyles when the knee is in flexion
- Full range of motion is retained
OD may be difficult to differentiate from osteonecrosis, but young patients are much more likely to have OD.
- Initial test
- May be normal in early stages
- More advanced lesions appear as a subchondral bony fragment surrounded by radiolucency.
Osteochondritis dissecans is a radiographic diagnosis.
- Conservative therapy: first-line treatment
- Arthroscopic extraction of the intra-articular loose fragment
- Other options depend on the stage and size of lesion, as well as skeletal maturity.