Patellar Dislocation

  • Steven F. DeFroda


Instability of the patella is a common and often unrecognized cause of knee pain in the adolescent patient and involves varying degrees of lateral patellar translation relative to the femoral trochlea (Khan et al. Anterior knee pain and patellar instability, Springer, London, 2011; DeFroda et al. J Pediatr 173:258–258.e1, 2016). Causes of instability include connective tissue disorders, developmental dysplasias, and trauma. Although some patients recall a specific traumatic event, others may not, which requires the diagnosis to be made on physical exam and imaging. The peak incidence of patellar dislocation occurs between the ages of 15 and 19 years old, with a rate of 11.19 per 100,000 person-years (Waterman et al. J Knee Surg. The rate of acute patellar dislocations are 33% higher in females than males and the risk of recurrent injuries is three times higher in girls (Fithian, Am J Sports Med 32:1114–1121, 2004). First-line management of patellar instability without fracture or loose body is conservative consisting of immobilization in slight flexion for 4–6 weeks with a knee immobilizer or hinged knee brace followed by physical therapy (Chotel et al. Orthop Traumatol Surg Res 100(1S):S125–S137, 2014). If nonoperative management fails (i.e., the patient has recurrent dislocation), there are many types of surgical reconstruction options available (Chotel et al. Orthop Traumatol Surg Res 100(1S):S125–S137, 2014).


Patellar dislocation MPFL Q angle Miserable malalignment Trochlear dysplasia 


  1. 1.
    Khan N, Fithian D, Nomura E. In: Sanchis-Alfonso V, editor. Anterior knee pain and patellar Inestability. London: Springer; 2011. Scholar
  2. 2.
    DeFroda SF, Hodax JD, Cruz AI. Patellar instability. J Pediatr. 2016;173:258–258.e1. Scholar
  3. 3.
    Waterman BR, Belmont PJ, Owens BD. Patellar dislocation in the United States: role of sex, age, race, and athletic participation. J Knee Surg. Published 2012. Accessed 27 Nov. 2015.Google Scholar
  4. 4.
    Fithian DC. Epidemiology and natural history of acute patellar dislocation. Am J Sports Med. 2004;32(5):1114–21. Scholar
  5. 5.
    Chotel F, Bérard J, Raux S. Patellar instability in children and adolescents. Orthop Traumatol Surg Res. 2014;100(1 S):S125–37. Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Steven F. DeFroda
    • 1
  1. 1.Department of Orthopaedic SurgeryWarren Alpert Medical School of Brown UniversityProvidenceUSA

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