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.
- Osteochondritis: painful inflammation of the cartilage and/or bone
- Osteochondritis dissecans: focal, aseptic necrosis of subchondral bone caused by mechanical stress and/or repetitive trauma
The etiology is unknown. Proposed theories include mechanical stress and repetitive trauma.
- Repeated trauma to area of subchondral hypovascularity → region of osteonecrosis → insufficient revascularization of necrotic bone → progressive subchondral bone lesion → partial or total detachment (“dissection”) of the subchondral bone and intraarticular cartilage fragment
- 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
Patients typically retain the full range of motion in the affected joint.
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.
- Used for early diagnosis in patients with persistent symptoms and normal x-rays and for precise staging
- May show articular cartilage thickening or partial detachment in early stages
Osteochondritis dissecans is a radiographic diagnosis.
Conservative therapy: first-line treatment
- Conservative therapy may be attempted first in patients who do not have detached or displaced intra-articular fragments.
- Children are more likely to improve with conservative management than adults.
- Initially, rest and limited physical activity
- Physical therapy
- Children with completely detached and displaced intra-articular fragments
- Children who have not responded to 4–6 months of conservative therapy
- Most adult patients with OD, although conservative therapy can be attempted for small or stable lesions
- Arthroscopic extraction of the intra-articular loose fragment
- Other options depend on the stage and size of lesion, as well as skeletal maturity.
- Drilling into the bone
- Fixation with pins or screws with bioabsorbable fixation for loose and non-displaced fragments
- Bone cartilage or chondrocyte transplantation