Patella dislocation: Difference between revisions

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==Background==
==Background==
*Occurs with trauma to an extended knee with externally rotated foot and twisting motion<ref>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</ref>
[[File:Knee diagram2.png|thumb|Anatomy of anterolateral aspect of right knee.]]
*Acute: in traumatic injury, occurs equally in men/women <ref name="epi">Fithian DC, Paxton EW, Stone ML, Silva P, Davis DK, Elias DA, White LM. Epidemiology and natural history of acute patellar dislocation. AJSM 2004;32:1114-1121</ref>
*Usual mechanism is blow to extended knee with externally rotated foott<ref>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</ref>
*Chronic: women/teenage girls<ref name="epi"></ref>
*May also occur with sudden lateral cut or twisting at the ankle or knee
*Commonly lateral displacement and unable to extend knee
*Acute traumatic dislocations more common in males<ref name="epi">Fithian DC, Paxton EW, Stone ML, Silva P, Davis DK, Elias DA, White LM. Epidemiology and natural history of acute patellar dislocation. AJSM 2004;32:1114-1121</ref>
*Chronic dislocation seen more commonly in women/teenage girls, typically little or no swelling<ref name="epi"></ref>
**May be associated with hemarthrosis
*Chronic dislocation more common in females
**Typically little or no swelling


==Clinical Features==
==Clinical Features==
[[File:Patellar dislocation.jpg|thumb|patella dislocates laterally]]
[[File:Patellar dislocation.jpg|thumb|patella dislocates laterally]]
*Patella is usually displaced laterally; knee is held in flexion
*Patella usually displaced laterally
*Acute: often with large hemarthrosis
*Knee held in flexion
*Chronic: little to no swelling
*Pain


==Differential Diagnosis==
==Differential Diagnosis==
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==Evaluation==
==Evaluation==
[[File:Patellaluxation ap 001.png|thumb]]
[[File:Patellaluxation ap 001.png|thumb]]
*Xray if traumatic mechanism to rule out fracture
*Clinical diagnosis
*Do not need xay prior to reduction if chronic
*May consider pre-reduction x-ray if concern for fracture (not required)
*Post-reduction x-ray: confirm reduction, eval for fractures and loose bodies (avulsions, misalignment, etc)<ref>Krause E A. et al. Pediatric lateral patellar dislocation: is there a role for plain radiography in the emergency department? J Emerg Med. 2013 Jun;44(6):1126-31</ref>
*Common associated fractures
**Medial patella facet
**Lateral femoral condyle


==Management==
==Management==
[[File:Patellar Dislocation Relocation.jpg|thumb|Relocation with lateral pressure on dislocated patella]]
[[File:Patellar Dislocation Relocation.jpg|thumb|Relocation with lateral pressure on dislocated patella]]
*Reduce; do not need x-rays prior to reduction.  Rarely need any sedation though a dose of IV pain medication can help relax the patient
*Reduce
**Option #1:
**Generally do not need x-rays prior to reduction
***Mild flexion of hip (20-30 degrees by raising head of bed, not by propping the leg up off the bed) to relax quadriceps
**Sedation rarely required
***Slowly extend and slightly hyperextend the knee and slide patella back into place.
***Single dose of pain medication may facilitate relaxation
**Option #2
 
***One provider applies slow downward pressure over the quads.  This stretches out the muscle and slowly straigtens the leg
===Techniques for closed reduction===
***At the same time, second pulls gentle traction of the patella outward while rotating the patella back over from lateral to anterior
 
**Knee immobilizer, NSAIDs, weight-bearing as tolerated
*Single operator
**Orthopedic follow-up within 1-2wks
#Place the hip in mild flexion by raising head of bed
*Unable to reduce or loose bodies/fracture on post-reduction imaging
#*This facilitates relaxation of the quadriceps
**Obtain immediate ortho consult
#Gently extend the knee with one hand while pushing the patella back in place with the other hand
 
*Two operators
#One provider applies slow downward pressure over quadriceps
#*This stretches the muscle and slowly straightens the leg
#Second provider gently rotates the patella lateral to anterior
 
*Place patient in knee immobilizer
*Provide NSAIDs
*Obtain radiographs to rule out associated fracture (consider including sunrise view)
*Allow weight-bearing as tolerated
 
==Complications==
*Commonly associated fractures:
**Medial patellar facet
**Lateral femoral condyle


==Disposition==
==Disposition==
*If unable to reduce or if fracture or loose bodies (i.e. osteochondral fracture) are seen on post-reduction radiographs, consult orthopedic surgery
*If patella successfully reduced, discharge with knee immobilizer and orthopedic follow up within 1 - 2 weeks


==References==
==References==

Revision as of 21:42, 21 May 2020

Background

Anatomy of anterolateral aspect of right knee.
  • Usual mechanism is blow to extended knee with externally rotated foott[1]
  • May also occur with sudden lateral cut or twisting at the ankle or knee
  • Acute traumatic dislocations more common in males[2]
  • Chronic dislocation seen more commonly in women/teenage girls, typically little or no swelling[2]
    • May be associated with hemarthrosis
  • Chronic dislocation more common in females
    • Typically little or no swelling

Clinical Features

patella dislocates laterally
  • Patella usually displaced laterally
  • Knee held in flexion
  • Pain

Differential Diagnosis

Knee diagnoses

Acute knee injury

Nontraumatic/Subacute

Evaluation

Patellaluxation ap 001.png
  • Clinical diagnosis
  • May consider pre-reduction x-ray if concern for fracture (not required)

Management

Relocation with lateral pressure on dislocated patella
  • Reduce
    • Generally do not need x-rays prior to reduction
    • Sedation rarely required
      • Single dose of pain medication may facilitate relaxation

Techniques for closed reduction

  • Single operator
  1. Place the hip in mild flexion by raising head of bed
    • This facilitates relaxation of the quadriceps
  2. Gently extend the knee with one hand while pushing the patella back in place with the other hand
  • Two operators
  1. One provider applies slow downward pressure over quadriceps
    • This stretches the muscle and slowly straightens the leg
  2. Second provider gently rotates the patella lateral to anterior
  • Place patient in knee immobilizer
  • Provide NSAIDs
  • Obtain radiographs to rule out associated fracture (consider including sunrise view)
  • Allow weight-bearing as tolerated

Complications

  • Commonly associated fractures:
    • Medial patellar facet
    • Lateral femoral condyle

Disposition

  • If unable to reduce or if fracture or loose bodies (i.e. osteochondral fracture) are seen on post-reduction radiographs, consult orthopedic surgery
  • If patella successfully reduced, discharge with knee immobilizer and orthopedic follow up within 1 - 2 weeks

References

  1. 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
  2. 2.0 2.1 Fithian DC, Paxton EW, Stone ML, Silva P, Davis DK, Elias DA, White LM. Epidemiology and natural history of acute patellar dislocation. AJSM 2004;32:1114-1121

See Also

Knee (Main)