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Osteochondritis dissecans

Definition

  • A condition whereby a segment of cartilage with subchondral bone separates from the articular surface

Incidence

  • most common in the knee
  • usually unilateral
  • imost common cause of a loose body in the knee joint of a young person
  • 15-20 knees / 100,000
  • more common in males
  • in the 2nd decade

Aetiology

  • 2 schools of thought
    • 1. due to an area of bone infaction with subsequent separation of a fragment
    • 2. due to an osteochondral fracture which fails to heal
      • this has been supported by
        • occurrence of OCD especially in athletic young people
        • associated with trauma to the joint e.g. direct blow, patellar dislocation
        • production of OCD lesions in cadavic knees by applying axial compression & rotatory forces
        • cadaveric studies showing that direct blow to the flexed knee can produce the classic OCD lesion at the lateral MFC

Associations

  • significant valgus or varus deformity - 14%
  • ACL deficiency - 7%
  • patellar subluxation/ dislocation - 16%

History

  • pain often activity related, usually of low intensity

Examination

  • wasting,
  • tenderness over the lesion,
  • joint effusion

Wilsons sign

    • flex knee to 90°
    • internally rotate tibia
    • slowly extend the knee- in patients with OCD
    • pain is produced at ~ 30° of flexion & is relieved with lateral rotation

Investigations

Xrays

  • AP/ Lateral/Tunnel
    • lesions most common on lateral aspect of MFC & posterior part of LFC
    • rare on the patella & the trochlea

CT

MRI

Arthoscopy

 

Natural History

  • Children
    • readily heals especially if on the posterior surface of the condyles
  • Not all lesions spontaneously heal
    • unstable
    • lesions in the classical lateral MFC position
      • less than 50% heal spontaneously

Treatment

  • Depends on
    • age of patient,
    • stage of disease
    • size & location of the lesion

Nonoperative

  • Indication
    • if lesion is intact & nontender
      • observation
      • rest
      • analgesia
    • if tender
      • splintage with R.O.M. exercises

Operative

  • indication
    • if symptomatic despite nonoperative treatment
    • displacement at any age
    • persistence after physeal closure
  • options
    • if cartilage intact
      • simple drilling of fragment with 1mm K- wire
    • loose or sequestered lesions
      • should be replaced & fixed
      • if lesion small e.g. < 5mm can excise

Prognosis

  • incidence of Osteoarthritis higher
    • in patients diagnosed & treated after skeletal maturity
    • large fragment excised