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Recognition and initial management of lateral patellar dislocations

Brian R Moore, MD
Joan Bothner, MD
Section Editors
Anne M Stack, MD
Albert C Hergenroeder, MD
Allan B Wolfson, MD
Deputy Editor
James F Wiley, II, MD, MPH


Lateral patellar dislocation occurs most often in the second and third decades of life [1-3]. The usual mechanism of injury is a twisting movement about the flexed knee as may occur during dancing, gymnastics, or the swinging of a baseball bat [4,5]. Direct trauma to the knee also may cause patellar dislocation. Lateral dislocation is most common; other types of patellar dislocations, including intra-articular dislocations, are rare [1,6]. (See 'Terminology' below and 'Mechanisms of injury' below.)

The clinical manifestations, diagnosis, and management of lateral patellar dislocations are reviewed here. Knee (tibiofemoral dislocations) and other knee injuries in young athletes are discussed separately. (See "Knee (tibiofemoral) dislocation and reduction" and "Approach to acute knee pain and injury in children and skeletally immature adolescents" and "Approach to chronic knee pain or injury in children or skeletally immature adolescents".)


Patellar dislocation is distinct from patellar subluxation or knee dislocation as follows:

Patellar dislocation – Patellar dislocations most commonly are lateral, although medial or superior dislocations are described. The patella is displaced from the trochlear groove. Intra-articular dislocations with lodging of the patella within the joint space may be superior, inferior, or vertical. (See 'Mechanisms of injury' below.)

Patellar subluxation – Patellar subluxation describes excessive lateral movement of the patella and may occur as a result of trauma or in patients with laxity. The patella still tracks within the trochlear groove but may cause discomfort and a feeling of instability. (See 'Anatomy' below.)


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Literature review current through: Sep 2016. | This topic last updated: Sep 28, 2015.
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  1. Cash JD, Hughston JC. Treatment of acute patellar dislocation. Am J Sports Med 1988; 16:244.
  2. Cofield RH, Bryan RS. Acute dislocation of the patella: results of conservative treatment. J Trauma 1977; 17:526.
  3. Atkin DM, Fithian DC, Marangi KS, et al. Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury. Am J Sports Med 2000; 28:472.
  4. Baskin MN. Injury-knee. In: Textbook of Pediatric Emergency Medicine, 5th, Fleisher GR, Ludwig S, Henretig FM. (Eds), Lippincott Williams & Wilkins, Philadelphia 2006. p.383.
  5. Patellofemoral instability and malalignment. In: Essentials of Musculoskeletal Care, 2nd, Green WB. (Ed), American Academy of Orthopedic Surgeons, Rosemont 2001. p.387.
  6. Young GM. Reduction of common joint dislocations and subluxations. In: Textbook of Pediatric Emergency Procedures, Henretig RM, King C. (Eds), Williams & Wilkins, Baltimore 1997. p.1088.
  7. Moore KL, Dalley AF, Agur AMR. Lower Limb. In: Clinically Oriented Anatomy, 6th edition, Wolters Kluwer | Lippincott Williams & Wilkins, Philadelphia 2010. p.636.
  8. Kocher MS. Intra-articular injuries of the knee. In: Rockwood And Wilkins' Fractures In Children, 7th edition, Beaty JH, Kasser JR. (Eds), Wolters Kluwer | Lippincott, Williams & Wilkins, Philadelphia 2010. p.900.
  9. Desio SM, Burks RT, Bachus KN. Soft tissue restraints to lateral patellar translation in the human knee. Am J Sports Med 1998; 26:59.
  10. Amis AA, Firer P, Mountney J, et al. Anatomy and biomechanics of the medial patellofemoral ligament. Knee 2003; 10:215.
  11. Beasley LS, Vidal AF. Traumatic patellar dislocation in children and adolescents: treatment update and literature review. Curr Opin Pediatr 2004; 16:29.
  12. Gakhar H, Singhal A. Superior dislocation of the patella: case report and review of the literature. J Emerg Med 2013; 44:478.
  13. Bassi RS, Kumar BA. Superior dislocation of the patella; a case report and review of the literature. Emerg Med J 2003; 20:97.
  14. Hughston JC, Deese M. Medial subluxation of the patella as a complication of lateral retinacular release. Am J Sports Med 1988; 16:383.
  15. Le Corroller T, Dediu M, Champsaur P. Transient medial patellar dislocation: injury patterns at US and MR imaging. Skeletal Radiol 2009; 38:519.
  16. McHugh G, Ryan E, Cleary M, et al. Intra-articular dislocation of the patella. Case Rep Orthop 2013; 2013:535803.
  17. Garner JP, Pike JM, George CD. Intra-articular dislocation of the patella: two cases and literature review. J Trauma 1999; 47:780.
  18. Maripuri SN, Mehta H, Mohanty K. Sleeve fracture of the superior pole of the patella with an intra-articular dislocation. A case report. J Bone Joint Surg Am 2008; 90:385.
  19. Shetty S, Ramesh B, Gul A, et al. Vertical dislocation of the patella: report of 2 cases. Orthopedics 2009; 32.
  20. Stefancin JJ, Parker RD. First-time traumatic patellar dislocation: a systematic review. Clin Orthop Relat Res 2007; 455:93.
  21. Hsiao M, Owens BD, Burks R, et al. Incidence of acute traumatic patellar dislocation among active-duty United States military service members. Am J Sports Med 2010; 38:1997.
  22. Sillanpää P, Mattila VM, Iivonen T, et al. Incidence and risk factors of acute traumatic primary patellar dislocation. Med Sci Sports Exerc 2008; 40:606.
  23. Mäenpää H, Lehto MU. Surgery in acute patellar dislocation--evaluation of the effect of injury mechanism and family occurrence on the outcome of treatment. Br J Sports Med 1995; 29:239.
  24. Seeley MA, Knesek M, Vanderhave KL. Osteochondral injury after acute patellar dislocation in children and adolescents. J Pediatr Orthop 2013; 33:511.
  25. Tolo V. Fractures and dislocations about the knee. In: Skeletal Trauma in Children, Green NE, Swiontkowski MF. (Eds), WB Saunders, Philadelphia 1998. p.453.
  26. Palmu S, Kallio PE, Donell ST, et al. Acute patellar dislocation in children and adolescents: a randomized clinical trial. J Bone Joint Surg Am 2008; 90:463.
  27. Rünow A. The dislocating patella. Etiology and prognosis in relation to generalized joint laxity and anatomy of the patellar articulation. Acta Orthop Scand Suppl 1983; 201:1.
  28. Larsen E, Lauridsen F. Conservative treatment of patellar dislocations. Influence of evident factors on the tendency to redislocation and the therapeutic result. Clin Orthop Relat Res 1982; :131.
  29. Mowery CA, Herring JA, Jackson D. Dislocated patella associated with below-knee amputation in adolescent patients. J Pediatr Orthop 1986; 6:299.
  30. Bollier M, Fulkerson JP. The role of trochlear dysplasia in patellofemoral instability. J Am Acad Orthop Surg 2011; 19:8.
  31. Steensen RN, Bentley JC, Trinh TQ, et al. The prevalence and combined prevalences of anatomic factors associated with recurrent patellar dislocation: a magnetic resonance imaging study. Am J Sports Med 2015; 43:921.
  32. Borochowitz Z, Soudry M, Mendes DG. Familial recurrent dislocation of patella with autosomal dominant mode of inheritance. Clin Genet 1988; 33:1.
  33. Carter, C. Sweetnam, R. Recurrent dislocation of the patella and of the shoulder: their association with familial joint laxity. J Bone Joint Surg 1960; 42B:721.
  34. Miller GF. Familial recurrent dislocation of the patella. J Bone Joint Surg Br 1978; 60-B:203.
  35. Stevens CA. Patellar dislocation in Rubenstein-Taybi syndrome. Am J Med Genet 1997; 72:188.
  36. Cooney AD, Kazi Z, Caplan N, et al. The relationship between quadriceps angle and tibial tuberosity-trochlear groove distance in patients with patellar instability. Knee Surg Sports Traumatol Arthrosc 2012; 20:2399.
  37. Köhlitz T, Scheffler S, Jung T, et al. Prevalence and patterns of anatomical risk factors in patients after patellar dislocation: a case control study using MRI. Eur Radiol 2013; 23:1067.
  38. Ogden JA. Knee. In: Skeletal Injury in the Child, Ogden JA. (Ed), Springer-Verlag, New York 2000. p.938.
  39. Lu DW, Wang EE, Self WH, Kharasch M. Patellar dislocation reduction. Acad Emerg Med 2010; 17:226.
  40. Bachman D, Santora S. Orthopedic trauma. In: Textbook of Pediatric Emergency Medicine, 3rd, Fleisher GR, Ludwig S, Henretig FM. (Eds), Lippincott Williams & Wilkins, Philadelphia 2006. p.1525.
  41. Krause EA, 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; 44:1126.
  42. Malanga GA, Andrus S, Nadler SF, McLean J. Physical examination of the knee: a review of the original test description and scientific validity of common orthopedic tests. Arch Phys Med Rehabil 2003; 84:592.
  43. Ahmad CS, McCarthy M, Gomez JA, Shubin Stein BE. The moving patellar apprehension test for lateral patellar instability. Am J Sports Med 2009; 37:791.
  44. Steiner T, Parker RD. Subluxation and dislocation - Patellofemoral instability: recurrent dislocation of the patella. In: Orthopedic Sports Medicine, 3rd, DeLee JC, Drez D, Miller MD. (Eds), Saunders, Philadelphia 2009. p.1548.
  45. Redziniak DE, Diduch DR, Mihalko WM, et al. Patellar instability. J Bone Joint Surg Am 2009; 91:2264.
  46. Ruddy RM. Illustrated techniques of pediatric emergency procedures. In: Textbook of Pediatric Emergency Medicine, 5th, Fleisher GR, Ludwig S, Henretig FM. (Eds), Lippincott Williams & Wilkins, Philadelphia 2006. p.1861.
  47. Ludwig S. Dislocations, subluxations, and diastasis. In: Illustrated Textbook of Pediatric Emergency and Critical Care Procedures, Dieckman RA, Fiser DH, Selbst SM. (Eds), Mosby, St. Louis 1997. p.630.
  48. Nietosvaara Y, Aalto K, Kallio PE. Acute patellar dislocation in children: incidence and associated osteochondral fractures. J Pediatr Orthop 1994; 14:513.
  49. Mäenpää H, Lehto MU. Patellar dislocation. The long-term results of nonoperative management in 100 patients. Am J Sports Med 1997; 25:213.
  50. Garrick JG, Webb DR. Knee injuries. In: Sport Injuries: Diagnosis and Management, 2nd, WB Saunders, Phladelphia 1992. p.259.
  51. Kibler WB. The knee. In: American College of Sports Medicine's Handbook for the Team Physician, Williams & Wilkins, Baltimore 1996. p.324.
  52. Panni AS, Vasso M, Cerciello S. Acute patellar dislocation. What to do? Knee Surg Sports Traumatol Arthrosc 2013; 21:275.
  53. Sillanpää PJ, Mattila VM, Mäenpää H, et al. Treatment with and without initial stabilizing surgery for primary traumatic patellar dislocation. A prospective randomized study. J Bone Joint Surg Am 2009; 91:263.