Patellar Dislocation

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We all like to feel like we can heal with our hands.  For this reason, simple reductions are sometimes welcome complaints in your ED that is filled with copious rhinorrhea and voluminous emesis.  We have discussed feeling like Mr. Miyagi during reductions of Nursemaid Elbows.  Another reduction that can make you feel similarly is the Patellar Dislocation, but before you bow as you exit the exam room, make sure that you aren’t being too cavalier.

Patellar Dislocation Basics

  • Acute patellar dislocation is a common knee injury.
  • Most often occurs in teenagers.
  • Most frequently associated with sports or physical activities.
  • Often seen when the femur rotates internally, the tibia rotates externally, and the foot is fixed.

Some Important Anatomy

  • The Medial Patellofemoral Ligament (MPFL)
    • Thin transverse band that extends from the femur to the medial aspect of the patella.
    • The MPFL is the primary ligamentous restraint for the patella.
      • It provides 50-60% of the restraining force.
    • The MPFL is ruptured in 94-100% of patients with acute patellar dislocation.
    • Repeat dislocation is dependent upon the MPFL injury rather than other predisposing factors (some listed below):
      • Lateral patellar tilt
      • Patella alta (abnormally high patella)
      • Trochlear dysplasia
      • Increased Q angle
      • Genu Valgum
      • Vastus Medialis Muscle hypoplasia
      • Increased femoral anteversion
      • Congenital conditions that lead to ligament laxity

Reduction of Patellar Dislocation

  1. Flex the Hip to relax the Quads.
  2. Apply medial pressure to the lateral edge of the dislocated patella.
  3. While continuing to apply medial pressure, extend the knee.

Imaging

  • Most typical patellar dislocations can be reduced without initial radiologic imaging.
  • Xrays will be needed, however, to help assess patellar location and assess for fractures afterwards.
  • MRI is also helpful in evaluating the MPFL (actually better than arthroscopy).
    • Naturally, this can occur as an outpatient through the Orthopaedic office.

What’s Next?

After you have done the Mr Miyagi part and feel like a superhero following the reduction, the patient/family will likely have some more questions.

  • It’s a good idea to keep the patient in a knee immobilizer until Ortho follow-up.
  • Discuss the potential for MRI based on the Orthopod’s preference.
  • Traditionally, conservative / non-operative management has been advocated for after 1st dislocation; however, there is a growing trend favoring reconstruction of the MPFL to help avoid a second dislocation.
    • This will be depend upon whether there are boney abnormalities (fractures, other anatomic anomalies) and the Orthopod’s preference.
    • It is a good idea to know that not all are treated conservatively anymore… just so you don’t misguide the family inadvertently.

 

References

Panni AS, Vasso M, Cerciello S. Acute patellar dislocation. What to do? Knee Surg Sports Traumatol Arthrosc. 2013 Feb;21(2):275-8. PMID: 23242381. [PubMed] [Read by QxMD]

Krause EA1, Lin CW, Ortega HW, Reid SR. Pediatric lateral patellar dislocation: is there a role for plain radiography in the emergency department? J Emerg Med. 2013 Jun;44(6):1126-31. PMID: 23357381. [PubMed] [Read by QxMD]

Seeley M1, Bowman KF, Walsh C, Sabb BJ, Vanderhave KL. Magnetic resonance imaging of acute patellar dislocation in children: patterns of injury and risk factors for recurrence. J Pediatr Orthop. 2012 Mar;32(2):145-55. PMID: 22327448. [PubMed] [Read by QxMD]

Sillanpää PJ1, Mattila VM, Mäenpää H, Kiuru M, Visuri T, Pihlajamäki H. Treatment with and without initial stabilizing surgery for primary traumatic patellar dislocation. A prospective randomized study. J Bone Joint Surg Am. 2009 Feb;91(2):263-73. PMID: 19181969. [PubMed] [Read by QxMD]

Stefancin JJ1, Parker RD. First-time traumatic patellar dislocation: a systematic review. Clin Orthop Relat Res. 2007 Feb;455:93-101. PMID: 17279039. [PubMed] [Read by QxMD]

Sean Fox

I enjoy taking care of patients and I finding it endlessly rewarding to help train others to do the same. I trained at the Combined Emergency Medicine and Pediatrics residency program at University of Maryland, where I had the tremendous fortune of learning from world renown educators and clinicians. Now I have the unbelievable honor of working with an unbelievably gifted group of practitioners at Carolinas Medical Center. I strive every day to inspire my residents as much as they inspire me.

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4 Responses

  1. April 4, 2014

    […] Continue reading here: Patellar Dislocation – Pediatric EM Morsels […]

  2. April 6, 2014

    […] Patellar Dislocation – Pediatric EM Morsels http://pedemmorsels.com/… factors (some listed below): Lateral patellar tilt; Patella alta (abnormally high patella); Trochlear dysplasia; Increased Q angle; Genu Valgum; Vastus Medialis Muscle hypoplasia; Increased femoral anteversion; Congenital conditions that lead to ligament laxity … Sillanpää PJ1, Mattila VM, Mäenpää H, Kiuru M, Visuri T, Pihlajamäki H. Treatment with and without initial stabilizing surgery for primary traumatic patellar dislocation. A prospective randomized study. J Bone … […]

  3. November 24, 2014

    […] Fox covers patellar dislocations for this week’s PED EM morsel. […]

  4. May 18, 2016

    […]  The majority of the injuries that we will manage are the more common orthopedic varieties (ex, Patellar Dislocation, Shoulder Dislocation, Supracondylar Fracture). Unfortunately, while we all want/need our children […]

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