Knee dislocation: Difference between revisions

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==Background==
==Background==
[[File:Knee diagram2.png|thumb|Anatomy of anterolateral aspect of right knee.]]
*[[Vascular injury|Popliteal artery injury]] is common
**About 25% of cases
**Neurologic deficit may indicate vascular injury
*Spontaneous reduction common
**About 50% self-reduce, usually en route to ED


===Types===
*Anterior (40%)
**Hyperextension
**Associated injuries to PCL, ACL, and medial or lateral ligaments common
*Posterior (33%)
**Usually due to impact with dashboard during motor vehicle collision
**Popliteal artery often injured
*Lateral (18%)
*Medial (4%)


Can result from high- or low-velocity injuries (MVC, martial arts, water-skiing)
==Clinical Features==
[[File:PMC2850837 wjem-11-103f1.png|thumb|The lateral view of the left knee showed a posterior knee dislocation.]]
*Instability in multiple directions
*Evidence of collateral ligamentous injury combined with peroneal nerve palsy
*History of high-energy mechanism
**Patients with BMI > 40 commonly report low-energy mechanism
*Affected knee may hyperextend relative to unaffected knee when leg is lifted by the foot


Anterior, posterior, medial, lateral, or rotatory dislocations all possible
===Associated Injuries===
*[[Vascular injury|Popliteal artery injury]]<ref>Tintinalli, J. E., Stapczynski, J. S., Ma, O. J., Yealy, D. M., Meckler, G. D., & Cline, D. (2016). Injuries to  Bones and Joints In Tintinalli's emergency medicine: A comprehensive study guide (Eighth edition.) (pp1863-1864). New York: McGraw-Hill Education.</ref>
**Cannot rule out based on normal distal pulses and Ankle Brachial Index (ABI) > 0.9
***Requires definitive vascular imaging or serial exams
*[[Peripheral nerve syndromes|Neurologic injuries]]
**Common peroneal nerve injury (25%)
***Test for:
****Sensation in 1st dorsal web space
****Dorsiflexion of foot
****Toe extension
**Tibial nerve injured (less common)
*[[Fractures]]
**Femur and tibia most common
**Check hip and ankle joints for associated fracture
**Avulsion fractures common
*[[Compartment syndrome]] risk high with vascular compromise


Anterior requires 30o of hyperextension before joint failure
==Differential Diagnosis==
{{Knee DDX}}


Posterior usually a dashboard injury
==Evaluation==
[[File:PosteriorKneeDIsclocation.jpg|thumb|Plain lateral X-ray of the left knee showing a posterior knee dislocation]]
[[File:Lateral-knee-dislocation-1.jpg|thumb|A lateral dislocation of the knee]]
[[File:CTAngioOcclusionRtPop.jpg|thumb|CT angiogram 3D reconstruction, posterior view showing a normal artery on the left, and occlusion to right popliteal artery as a result of a knee dislocation]]
*Knee x-ray (to rule-out fracture)
*Vascular assessment
**Assess popliteal and distal pulses
**Measure ABIs
***ABI >0.9 - serial exams
***ABI <0.9 - arterial duplexes or CT angio
**Hard Signs
***Observed pulsatile bleeding
***Arterial thrill by manual palpation
***Bruit over or near the artery by auscultation
***Signs of distal ischemia
***Visible expanding hematoma
**Soft Signs
***Significant hemorrhage found on history
***Decreased pulse compared to the other extremity
***Bony injury or proximal penetrating wound
***Neurologic abnormality
*Consider CT Angiography:
**Asymmetric pulses
**ABI <0.9
**Clinical concern of vascular injury (ischemia, hemorrhage, or expanding hematoma)


==Management==
*Reduce immediately
**Avoid additional arterial injury by limiting excessive force during reduction


==Pathophysiology==
===Posterior dislocation<ref name="Procedures for orthopedic emergencies">Davenport M. Procedures for orthopedic emergencies. In: Bond M, ed. Orthopedic Emergencies: Expert Management for the Emergency Physician. Cambridge: Cambridge University Press; October 31, 2013.</ref>===
#Grasp proximal tibia
#Have assistant grasp distal femur and provide gentle counter-traction
#Apply longitudinal traction to proximal tibia
#Move proximal tibia anteriorly
#Immobilize in 10-15 degrees of flexion
#Assess neurovascular status
#Obtain post-reduction imaging


===Anterior dislocation<ref name="Procedures for orthopedic emergencies">Davenport M. Procedures for orthopedic emergencies. In: Bond M, ed. Orthopedic Emergencies: Expert Management for the Emergency Physician. Cambridge: Cambridge University Press; October 31, 2013.</ref>===
#Grasp distal femur
#Have assistant grasp proximal tibia and provide gentle counter-traction
#Pull distal femur proximally
#Move distal femur anteriorly
#Immobilize in 10-15 degrees of flexion
#Assess neurovascular status
#Obtain post-reduction imaging


Requires failure of three ligaments


Popliteal artery injured in 20-30%; if high-velocity then 40%
*Monitor for [[compartment syndrome]]
**No pulses: reduce immediately
**No pulses post reduction: surgical exploration
***Ischemic time >8 hours has amputation rates as high as 86%


8 hour window...
==Disposition==
*Institution will dictate admission process
**Suggested algorithm
***If: Strong pulses + ABI >0.9 + normal doppler, admit for obs and serial vascular exams
***If: Good perfusion + asymmetric pulses or ABI <0.9 or abnormal doppler, consult vascular surgery + obtain CTA
***If: Weak pulses or signs of ischemia = emergent vascular surgery consult and OR
*Consider trauma consult depending on mechanism and additional injuries


==See Also==
*[[Knee (Main)]]
*[[Patella dislocation]]


==Physical Exam==
==External Links==
*Standard:  <https://emergencymedicinecases.com/occult-knee-injuries/>


==References==
<references/>


If dislocation is still present, joint injury is easy to diagnose
*Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
*AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
*Levy BA, Fanelli GC, Whelan DB, Stannard JP, MacDonald PA, Boyd JL, Marx RG, Stuart MJ. Knee Dislocation Study Group. Controversies in the treatment of knee dislocations and multiligament reconstruction. J Am Acad Orthop Surg. 2009 Apr;17(4):197-206. http://www.ncbi.nlm.nih.gov/pubmed/19307669


-Reduce if dislocated!
[[Category:Orthopedics]]
 
-Search for hard and soft vascular signs
 
-If hard vascular signs are present, popliteal artery injury is easy to diagnose
 
--Hard signs = Pulse deficits, ischemic limb, active hemorrhage, expanding/pulsatile hematoma
 
--Soft signs = Small/stable hematoma, injury to anatomically related nerve, history of hemorrhage
 
 
Considerations:-Knee may present already reduced
 
-Finding of significant ligament laxity
 
-NB: Rate of arterial injury is the SAME, regardless
 
-Knee swelling is NOT universal
 
--Knee capsule is frequently disrupted, allowing hemarthrosis to leak into surrounding tissues
 
-Normal pulses do NOT rule-out a vascular injury
 
--10% of vascular injuries have normal palpated pulses
 
 
==W/U==
 
 
-Xray
 
SOFT SIGNS
 
Requires further evaluation/studies
 
-ABI's
 
-Duplex Doppler Ultrasonography
 
--Reported sensitivity of 95% and specificity of 99%
 
--Can miss intimal tears (intimal tears > 30% ofvessel lumen are felt to be “significant”).
 
 
HARD SIGNS
 
OR +/- CT Angiogram prior
 
 
==Treatment==
 
 
Reduction, ortho, vascular consult if necessary
 
 
==Consequences==
 
 
Amputation rate:
 
>8h = 80%
 
<8h = 15%
 
 
 
 
[[Category:Ortho]]

Latest revision as of 16:16, 22 March 2023

Background

Anatomy of anterolateral aspect of right knee.
  • Popliteal artery injury is common
    • About 25% of cases
    • Neurologic deficit may indicate vascular injury
  • Spontaneous reduction common
    • About 50% self-reduce, usually en route to ED

Types

  • Anterior (40%)
    • Hyperextension
    • Associated injuries to PCL, ACL, and medial or lateral ligaments common
  • Posterior (33%)
    • Usually due to impact with dashboard during motor vehicle collision
    • Popliteal artery often injured
  • Lateral (18%)
  • Medial (4%)

Clinical Features

The lateral view of the left knee showed a posterior knee dislocation.
  • Instability in multiple directions
  • Evidence of collateral ligamentous injury combined with peroneal nerve palsy
  • History of high-energy mechanism
    • Patients with BMI > 40 commonly report low-energy mechanism
  • Affected knee may hyperextend relative to unaffected knee when leg is lifted by the foot

Associated Injuries

  • Popliteal artery injury[1]
    • Cannot rule out based on normal distal pulses and Ankle Brachial Index (ABI) > 0.9
      • Requires definitive vascular imaging or serial exams
  • Neurologic injuries
    • Common peroneal nerve injury (25%)
      • Test for:
        • Sensation in 1st dorsal web space
        • Dorsiflexion of foot
        • Toe extension
    • Tibial nerve injured (less common)
  • Fractures
    • Femur and tibia most common
    • Check hip and ankle joints for associated fracture
    • Avulsion fractures common
  • Compartment syndrome risk high with vascular compromise

Differential Diagnosis

Knee diagnoses

Acute knee injury

Nontraumatic/Subacute

Evaluation

Plain lateral X-ray of the left knee showing a posterior knee dislocation
A lateral dislocation of the knee
CT angiogram 3D reconstruction, posterior view showing a normal artery on the left, and occlusion to right popliteal artery as a result of a knee dislocation
  • Knee x-ray (to rule-out fracture)
  • Vascular assessment
    • Assess popliteal and distal pulses
    • Measure ABIs
      • ABI >0.9 - serial exams
      • ABI <0.9 - arterial duplexes or CT angio
    • Hard Signs
      • Observed pulsatile bleeding
      • Arterial thrill by manual palpation
      • Bruit over or near the artery by auscultation
      • Signs of distal ischemia
      • Visible expanding hematoma
    • Soft Signs
      • Significant hemorrhage found on history
      • Decreased pulse compared to the other extremity
      • Bony injury or proximal penetrating wound
      • Neurologic abnormality
  • Consider CT Angiography:
    • Asymmetric pulses
    • ABI <0.9
    • Clinical concern of vascular injury (ischemia, hemorrhage, or expanding hematoma)

Management

  • Reduce immediately
    • Avoid additional arterial injury by limiting excessive force during reduction

Posterior dislocation[2]

  1. Grasp proximal tibia
  2. Have assistant grasp distal femur and provide gentle counter-traction
  3. Apply longitudinal traction to proximal tibia
  4. Move proximal tibia anteriorly
  5. Immobilize in 10-15 degrees of flexion
  6. Assess neurovascular status
  7. Obtain post-reduction imaging

Anterior dislocation[2]

  1. Grasp distal femur
  2. Have assistant grasp proximal tibia and provide gentle counter-traction
  3. Pull distal femur proximally
  4. Move distal femur anteriorly
  5. Immobilize in 10-15 degrees of flexion
  6. Assess neurovascular status
  7. Obtain post-reduction imaging


  • Monitor for compartment syndrome
    • No pulses: reduce immediately
    • No pulses post reduction: surgical exploration
      • Ischemic time >8 hours has amputation rates as high as 86%

Disposition

  • Institution will dictate admission process
    • Suggested algorithm
      • If: Strong pulses + ABI >0.9 + normal doppler, admit for obs and serial vascular exams
      • If: Good perfusion + asymmetric pulses or ABI <0.9 or abnormal doppler, consult vascular surgery + obtain CTA
      • If: Weak pulses or signs of ischemia = emergent vascular surgery consult and OR
  • Consider trauma consult depending on mechanism and additional injuries

See Also

External Links

References

  1. ↑ Tintinalli, J. E., Stapczynski, J. S., Ma, O. J., Yealy, D. M., Meckler, G. D., & Cline, D. (2016). Injuries to Bones and Joints In Tintinalli's emergency medicine: A comprehensive study guide (Eighth edition.) (pp1863-1864). New York: McGraw-Hill Education.
  2. ↑ 2.0 2.1 Davenport M. Procedures for orthopedic emergencies. In: Bond M, ed. Orthopedic Emergencies: Expert Management for the Emergency Physician. Cambridge: Cambridge University Press; October 31, 2013.
  • Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
  • AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
  • Levy BA, Fanelli GC, Whelan DB, Stannard JP, MacDonald PA, Boyd JL, Marx RG, Stuart MJ. Knee Dislocation Study Group. Controversies in the treatment of knee dislocations and multiligament reconstruction. J Am Acad Orthop Surg. 2009 Apr;17(4):197-206. http://www.ncbi.nlm.nih.gov/pubmed/19307669
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