Patellar Dislocation

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Background

• Typically occurs with trauma to an extended knee with externally rotated foot (quick pivoting in basketball, football and soccer)
• Acute dislocation occurs with traumatic injury, M=F, may see hemarthrosis
• Chronic dislocation or patholaxity seen more commonly in women
  • Ehlers-Danlos syndrome
  • Typically, little or no swelling; painless
  • Recurrent subluxation episodes with each flexion movement
• May occur from a direct blow (ex. helmet to knee collision in football; knee-knee collision in basketball)
  • Usually on noncontact twisting injury with the knee extended and foot externally rotated
  • Patient will usually reflexively contract quadriceps thereby reducing the patella
• Common associated fractures
  • Medial patella facet
  • Lateral femoral condyle

 
Clinical Features

• Patella is usually displaced laterally
• Knee is held in flexion
• Acute dislocation usually associated with a large hemarthrosis   
  • Absence of swelling supports ligamentous laxity and chronic dislocation mechanism

 
Evaluation

• Clinical diagnosis
• May consider pre-reduction x-ray if concern for fracture (not required)

 
Management

• Reduction = Relocation with lateral pressure on dislocated patella
• Do NOT need x-rays prior to reduction
  • Consider XR following reduction to rule out fracture or loose body
• Rarely need any sedation (sub-dissociative dose ketamine ?)
• Option #1:
  • Mild flexion of hip (20-30 degrees by raising head of bed, not by propping the leg up off the bed) to relax quadriceps
  • Slowly extend and slightly hyperextend the knee and slide patella back into place.
• Option #2
  • One provider applies slow downward pressure over the quads. This stretches out the muscle and slowly straightens the leg
  • At the same time, second provider pulls gentle traction of the patella outward while rotating the patella back over from lateral to anterior

​Disposition

• Obtain ortho consult if unable to reduce or fracture/loose bodies seen on post-reduction x-ray
• Otherwise may be discharged with ortho follow-up in 1-2 weeks
• Non-Operative:
  • NSAIDS, activity modification, and physical therapy
  • Knee immobilizer for comfort (short-term)
  • Quad strengthening exercises
  • Core and hip strengthening to improve limb positioning and balance (hip abductors, gluteals, and abdominals) 
• Consider knee aspiration for tense effusion
  • Positive fat globules indicates fracture