Knee

Anterior Cruciate Ligament Tear

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Anterior Cruciate Ligament Tear, ACL Tear, Anterior Cruciate Deficiency, Anterior Cruciate Ligament Rupture, ACL Rupture

  • Epidemiology
  1. Common injury associated with Contact Sports
  2. Uncommon in children and younger teens
    1. Growth Plate injuries are more common in this age group due to relative weakness
  • Risk Factors
  1. Female Gender (Relative Risk: 1.4 to 9)
  2. Play intensity (risk increased >3 fold during games compared with practice)
  3. High risk sports
    1. Skiing or snow boarding (esp. ankles locked with fall backwards)
    2. Soccer (esp. sudden cutting maneuvers)
    3. Basketball
    4. Football
    5. Volleyball
  • Mechanism
  1. Contact Sport related injury (30% of ACL injuries)
    1. Foot planted or otherwise in fixed position
    2. Torque from a blow results in tearing of the ACL
  2. Knee hyperextension injury
    1. Occurs when sudden deceleration with knee fully extended
    2. Sudden foot plant with cut to opposite side
    3. Valgus stress causes tibial anterior displacement
    4. ACL Ruptures as tibia displaces anteriorly
  • Symptoms
  1. Painful "popping" sensation at time of injury
  2. Swelling (hemarthrosis) within 1-2 hours of injury
  3. "Giving way" or buckling sensation of knee
  • Exam
  1. See Knee Exam
  • Signs
  1. Hemarthrosis (loss of peri-Patellar groove)
    1. Typically develops within hours of injury and often limits the remainder of the Knee Exam
      1. Loss of hyperextension (due to torn ACL fragment catching) in the presence of hemarthrosis is most sensitive for ACL Tear
    2. Associated with significant pain, guarding and limited range of motion
    3. Acute Knee Injury and hemarthrosis in athletes is correlated with ACL Tear
      1. Hardaker (1990) South Med J 83(6):640-44 [PubMed]
  2. Anterior Cruciate Ligament (ACL) Stability Tests
    1. Lachman Test (highest Test Sensitivity approaching 84%)
    2. Knee Anterior Drawer Test (test sesitivity 62%)
    3. Pivot Shift Test - MacIntosh Test (Test Sensitivity 62%)
  • Associated Conditions
  1. Meniscal tear (>60% of cases)
  2. Collateral ligament tear (5-24% of cases)
  • Radiology
  1. Knee XRay (3 view)
    1. Evaluate for Tibial Spine Avulsion Fracture
      1. Treat with Knee Immobilizer and urgent orthopedic follow-up
    2. Evaluate for Segond Fracture
      1. Avulsion of lateral capsular margin of tibia
  2. Knee MRI
    1. Efficacy in detecting ACL Tear
      1. Test Sensitivity: 86%
      2. Test Specificity: 95%
      3. Crawford (2007) Br Med Bull 84:5-23 [PubMed]
    2. Indications
      1. Preparation for ACL reconstruction
      2. Assess pediatric patient with suspected ACL Tear
  • Management
  • Conservative
  1. Quadriceps strengthening Exercises
  2. Knee Brace
  3. Activity modification
    1. Avoid cutting sports
    2. Avoid jumping sports
  • Management
  • Adults Surgical ACL Reconstruction
  1. Acute surgical repair is associated with poor results
  2. Athletic patient
    1. Participating in "cutting" or jumping sports
  3. Requires 9-12 weeks of rehabilitation post-operatively
  4. Bracing after ACL repair is not effective
    1. Does not prevent reinjury or speed recovery
    2. McDevitt (2004) Am J Sports Med 32:1887-92 [PubMed]
  • Management
  • Children
  1. Non-displaced Type I Avulsion Fracture
    1. Long-leg Cast Immobilization for 4-6 weeks
  2. Displaced Type II to III Avulsion Fractures
    1. Open Reduction and Internal Fixation
    2. Long-leg Cast Immobilization for 4-6 weeks
  3. Intrasubstance Tears
    1. Operative Management
      1. Indicated for older children near skeletal maturity
    2. Non-operative Management (See above)
      1. Indicated in Young Children (Open Growth Plates)
      2. Perform operative reconstruction when mature
  • Complications of Un-repaired ACL
  • Prevention
  • Athletes
  1. Enhance Performance Program
    1. Reduces ACL injuries by >75%
    2. Focuses on neuromuscular training and proprioception Exercises
    3. Mandelbaum (2005) Am J Sports Med 33(7): 1003-10 [PubMed]