Meniscus and ligament knee injuries

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Background

  • Anterior Cruciate Ligament
    • Limits anterior translation of tibia
    • 75% of all hemarthroses are caused by disruption of ACL
  • Posterior Cruciate Ligament
    • Limits posterior translation of tibia
    • Isolated injuries are rare
  • Medial Collateral Ligament
    • Provide restraint against valgus (outward) stress
  • Lateral Collateral Ligament
    • Provide restraint against varus (inward) stress

Clinical Features

ACL

  • Hearing/feeling a "pop" during injury with ensuing knee instability is pathognomonic
  • Anterior Drawer Sign
    • Pt supine, knee flexed 90', attempt to displace tibia from femur in a forward direction
    • Displacement of >6mm compared w/ opposite knee indicates injury
  • Lachman Test (most sensitive)
    • Pt supine, knee flexed 30', femur held w/ one hand, prox tibia pulled up w/ other hand
    • Displacement >5mm or soft end-point indicates injury
  • Pivot Shift Test
  • Segond Fracture
    • Pathognomonic for ACL tear but rare

PCL

  • Posterior Drawer Sign
    • Patient supine, knee flexed 90', attempt to displace tibia from femur in backward direction

Meniscus

  • Symptoms
    • "Locking" of joint or sensation of popping, clicking, or snapping
  • Signs
    • Effusions that occur after activity
    • Joint-line tenderness
  • Tests
    • McMurray, grind test only 50% Sn

Differential Diagnosis

Knee diagnoses

Acute Injury

Nontraumatic/Subacute

Evaluation

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Segond Avulsion Fracture (ACL tear)
  • Knee XR to rule-out fracture
  • Normally clinically diagnosed initially or referred for re-exam in 4-5 days after decrease of swelling
    • Primary medical doctor or orthopedics may later use MRI for definitive diagnosis

Management

  • Knee brace, ice, elevation, ambulation as soon as comfortable
    • Full knee immobilization generally not indicated for single ligament injuries
  • Ortho referral

See Also

References