II. Epidemiology

  1. Knee is most common site for Osteochondritis Dissecans
  2. Incidence: 30 to 60 per 100,000
  3. Bilateral knee involvement in 30 to 40%
  4. Males affected 3 times more often than females
  5. Peak Incidence
    1. Children under age 12 years
    2. Young adults
  6. Often missed at time of injury when it occurs
    1. Found later on Knee XRay

III. Pathophysiology

  1. Avascular subchondral bone necrosis
  2. Articular fragments may also separate

IV. Types: Sites involved

  1. Medial femoral condyle (80 to 85%)
    1. Lateral aspect most often affected
  2. Lateral femoral condyle (10 to 15%)
  3. Patella (5%)

V. Symptoms

  1. Poorly localized aching Knee Pain and swelling
  2. Knee locking, catching or giving-way sensation
    1. Occurs if loose body present
  3. Morning stiffness
  4. Knee Effusion may be recurrent
  5. Knee Pain provocative factors
    1. Strenuous activity
    2. Twisting knee motion (tibia internal rotation)

VI. Signs

  1. Full knee range of motion
  2. Quadriceps atrophy on affected side
    1. Decreased thigh circumference
  3. Tenderness at affected femoral condyle with knee flexed
  4. Wilson Test

VII. Imaging

  1. Knee XRay (AP, Lateral, PA Tunnel and Merchant View)
    1. Subchondral bone defect at sites above
    2. Loose body may be present
  2. Bone scan
  3. Knee MRI

VIII. Management: Conservative (esp. if Growth Plates open)

  1. Relative rest initially for 1-2 weeks
    1. Knee Immobilization
    2. Minimal weight bearing
  2. Modify activity level for 6 to 12 weeks
    1. Avoid rapid or strenuous activity (High Impact)
      1. Running
      2. Cutting
      3. Jumping
    2. Consider low impact alternative Exercises
      1. Bicycling
      2. Swimming
    3. No modification to upper body Exercise and ADLs
  3. Criteria for return to full activity
    1. No subjective pain
    2. Normal physical exam
    3. XRay shows signs of heeling
  4. Isometric quadriceps Exercises
  5. Anticipate healing over time
  6. Surgical arthrotomy or arthroscopic surgery
    1. Indicated if Fracture fragments > 1 cm diameter
    2. Lateral femoral condyle

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