Rosen & Barkin's 5-Minute Emergency Medicine Consult (410 page)

• Narcotic analgesia IV
  
• Avoid PO meds, as surgery may be necessary.
  

FOLLOW-UP

All patients require admission for observation of limb perfusion and PA repair if necessary.

All patients should be admitted.

Eventual repair of ligamentous injuries:

• Usually at 3 wk
  
• Arthroscopic surgery is contraindicated for 2 wk after injury to prevent compartment syndrome.
  

• Orthopedics for ligamentous repair
  
• Vascular for PA injury
  

• Failure to revascularize PA within 6–8 hr: Amputation rate approaches 90%.
  
• Peroneal nerve injury:
  
  • Poor prognosis for recovery
    
• Delayed compartment syndrome may occur.
  

• Kelleher HB, Mandavia D. Dislocation, knee.
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  www.emedicine.medscape.com/article/823589-overview
  
• Mills WJ, Barei DP, McNair P. The value of ankle-brachial index for diagnosing arterial injury after knee dislocation: A prospective study.
  J Trauma
  . 2004;56(6):1261–1265.
  
• Nicandri GT, Chamberlain AM, Wahl CJ. Practical management of knee dislocations: A selective angiography protocol to detect limb-threatening vascular injuries.
  Clin J Sport Med
  . 2009;19(2):125–129.
  
• Seroyer ST, Musahl V, Harner CD. Management of the acute knee dislocation: The Pittsburgh experience.
  Injury
  . 2008;97(7):710–718.
  

CODES

• 836.50 Dislocation of knee, unspecified, closed
  
• 836.51 Anterior dislocation of tibia, proximal end, closed
  
• 836.52 Posterior dislocation of tibia, proximal end, closed
  

BASICS

• Cruciate ligament injuries:
  
  • Anterior cruciate ligament (ACL):
    
    • From the posteromedial aspect of the lateral femoral condyle to the intraspinus area on the tibia
      
    • Prevents excessive anterior translation of the tibia, internal rotation of the tibia on the femur, or hyperextension of the knee.
      
  • Posterior cruciate ligament (PCL):
    
    • Twice as strong and twice as thick as the normal ACL, less commonly injured
      
    • From anterolateral aspect of medial femoral condyle to the posterior tibia
      
• Meniscal tears:
  
  • Medial meniscus injury most common
    
    • More firmly attached to the joint capsule and less mobile than lateral meniscus
      
  • Tears are the result of tensile or compressive forces between the femoral and tibial condyles
    
  • Extension of meniscal tear may result in a free segment that may become displaced into the joint, resulting in a true locked joint.
    
• Medial collateral ligament:
  
  • From the posterior aspect of medial femoral condyle to the tibia, distal to joint
    
  • Often accompanied by other injury:
    
    • Hyperextension with external rotation (ACL/PCL injured 1st)
      
    • Anterior stress (ACL injured 1st)
      

• ACL:
  
  • Most commonly injured knee ligament
    
  • 200,000 ACL injuries annually in US
    
  • 2/3 of all ACL injuries are noncontact
    
  • Female gender: 3× greater risk
    
• Associated injuries:
  
  • ∼50% ACL injuries are associated with meniscal tears
    
  • ACL injuries commonly have chondral and subchondral injuries
    
• Meniscus:
  
  • Medial meniscus injury 10× more common than lateral
    
  • True locked joint in only 30%
    

• Cruciate ligament injuries:
  
  • ACL: Often deceleration with flexion and rotation, or hyperextension
    
    • Usually sports-related, especially skiing and football
      
    • Plant-and-pivot or stop-and-jump mechanism
      
  • PCL:
    
    • “Dashboard injury”: Flexed knee with posteriorly directed force to the anterior proximal tibia (motor vehicle crash or direct trauma)
      
    • Fall on flexed knee
      
• Meniscus Injury:
  
  • Sudden rotary motion of knee associated with squatting, pivoting, turning, and bending
    
  • Common in sports with low stance positions (wrestling/football) or kneeling position (carpet installers, plumbers)
    
• Medial collateral ligament injuries:
  
  • Direct trauma to lateral knee
    
  • Most common: Valgus stress with external rotation on flexed knee:
    
    • From catching a ski tip
      
    • Side tackle (football)
      

• The ACL is the most frequently injured knee ligament in children.
  
• Isolated MCL injury infrequent before growth plate closure (<14-yr old)
  

DIAGNOSIS

• Cruciate ligament injuries:
  
  • Feeling knee “give way,” pop, tearing sensation
    
  • Most patients report immediate knee dysfunction, but some may ambulate despite complete ACL rupture because of stability from supporting structures.
    
  • Large, almost immediate effusion -- patients report significant swelling
    
• Medial collateral ligament:
  
  • Tearing sensation and immediate pain in medial aspect of knee
    
  • Medial pain and tenderness may be more pronounced with partial tears than with complete tears.
    
• Medial meniscus injury:
  
  • Patient may recall the knee “giving way”
    
  • Inability to fully extend knee is common
    
  • Effusion is found in 50% and usually occurs over 6–12 hr.
    
  • Pain is often intermittent and localized to the joint line
    
  • Unlike ligamentous injury, patients often report completion of activities at time of injury
    
  • Degenerative meniscal tears tend to have a more insidious, atraumatic presentation, with mild swelling, vague joint line pain, and sometimes with mechanical symptoms. Often associated with osteoarthritis.
    

• Ability to bear weight reduced with all injuries
  
• Palpate for pain on:
  
  • bony prominences for fracture
    
  • growth plates in children
    
  • medial and lateral joint line (meniscus and collateral ligament injury)
    
• Range of motion:
  
  • Locking: May occur with ACL (interposition of torn cruciate), meniscus injury, loose body (arthritis)
    
  • Pseudolocking may be present from pain, effusion, or spasm
    
• Effusion:
  
  • Immediate (within 2–3 hr) usually indicates a significant intra-articular injury including ACL
    
  • About 70% of acute knee hemarthroses are caused by ACL injury, but lack of effusion does not rule out ACL injury
    
  • MCL, meniscus, PCL injuries have more delayed effusion (12–24 hr)
    
  • Warmth, erythema: Consider infection
    
• Neurovascular exam:
  
  • Distal pulses
    
  • 1st dorsal web-space sensation (deep peroneal nerve)
    
  • Ankle/toe dorsiflexion
    
• Stress testing:
  Always compare the injured to the uninjured side
  (asymmetry is more reliable than absolute degree of laxity):
  
  • Pain and spasm can limit the utility of all stress testing in the acute phase
    
  • Lachman test
    is most reliable for ACL:
    
    • Knee flexed 20°, patient supine with thigh supported and hip slightly externally rotated. Quickly bring the tibia forward on the femur, 1 hand holding proximal tibia, the other stabilizing the femur just above the patella, evaluating for quality of the endpoint and degree of anterior translation of the tibia
      
    • Pain with motion = partial tear or disruption
      
    • Quantification of degree of movement less important then simply positive or negative interpretation of test
      
  • Pivot shift test:
    More specific for ACL injury but unreliable without anesthesia and painful acutely. Not recommended routinely in the ED.
    
  • Anterior/posterior drawer sign
    :
    
    • Knee flexed 90°, patient supine, hip flexed 45°, foot neutral and stabilized (sit on foot)
      
    • Observe for posterior sag of tibia, positive with PCL injury
      
    • Posterior drawer (PCL): Movement of tibia back with application of posterior pressure
      
    • Anterior drawer (ACL): Movement of tibia forward with anterior distraction force
      
  • Quadriceps active test (PCL):
    
    • Patient supine, knee flexed at 90°, hip flexed at 45°
      
    • Patient attempts to extend knee against examiner’s counterforce
      
    • Positive if the tibia translates anteriorly during quad activation
      
  • Varus/valgus stress testing: Evaluate in extension and 20° flexion for MCL and LCL laxity
    
• Meniscus: Wait until acute pain is controlled:
  
  • McMurray
    : While palpating joint lines, extend the knee while internally and then externally rotating. Pain and click is positive.
    
  • Apley
    : With patient prone, flex knee to 90°, provide axial load and internally/externally rotate lower leg. Pain is positive.