Osteochondritis Dissecans

Snapshot

• A 13-year-old boy presents with left knee pain. He reports that he cannot specifically localize where the pain is in the left knee but has noticed it has progressively worsened over the course of 7 months. He also says that knee swelling typically appears after he plays basketball. On physical exam, there is mild swelling on the left knee. With the left knee in the flexed position with pressure over the medial femoral condyle, there is tenderness to palpation. Range of motion of the knee is intact. An anterior-posterior radiograph of the affected knee demonstrates crescent-shaped radiolucency surrounding subchondral bony fragments.

Introduction

• Clinical definition
  • osteonecrosis of subchondral bone
• Epidemiology
  • incidence
    • rare
    • 15-29 cases per 100,000 patients
  • demographics
    • males > females
    • age
      • 10-20 years of age
  • risk factors
    • African American race
    • repeated trauma and overuse
• Etiology
  • unknown but may be due to
    • recurring micro-trauma
    • ischemic injury
• Pathogenesis
  • initial trauma leads to necrosis which places the patient at risk for
    • chondromalacia
    • fracture
    • necrotic bone absorption
  • note that revascularization is required to heal the subchondrial bone
    • when this revascularization is impaired osteochondritis dissecans ensues
• Prognosis
  • skeletally immature patients are more likely to have a complete recovery than skeletally mature patients
• patients with less severe lesions are more likely to have a complete recovery

Presentation

• Symptoms 
  • knee, elbow, or ankle pain
    • worsens with physical activity
  • stiffness
  • swelling
• Physical exam
  • full range of motion is usually found with knee involvement
  • tenderness to palpation
• crepitus may be found

Imaging

• Radiography
  • indication
    • initial imaging test for patient suspected to have osteochondritis dissecans
  • findings
    • early lesions may appear normal
• advanced lesions may demonstrate subchondral flattening and radiolucency at the cortical surface 

Studies

• Diagnostic criteria
• diagnosis is based on clinical presentation and plain radiography of the affected area

Differential

• Avascular necrosis

Treatment

• Conservative
  • restrict physical activity, immobilization, and physical therapy
    • indication
      • first-line for less severe osteochondritis dissecans
• Operative
  • orthopedic surgery
    • indication
      • those who are unresponsive to conservative management
• severe osteochondritis dissecans

Complications

• May progress to osteoarthritis of the affected join