Knee Surgery, Sports Traumatology, Arthroscopy

, Volume 22, Issue 10, pp 2308–2314 | Cite as

Which patellae are likely to redislocate?

  • Peter BalcarekEmail author
  • Swantje Oberthür
  • Stephanie Hopfensitz
  • Stephan Frosch
  • Tim Alexander Walde
  • Martin Michael Wachowski
  • Jan Philipp Schüttrumpf
  • Klaus Michael Stürmer



The purpose of this study was to identify the risk factors for recurrent lateral patellar dislocations and to incorporate those factors into a patellar instability severity score.


Sixty-one patients [male/female 35/26; median age 19 years (range 9–51 years)] formed the study group for this investigation. Within the study group, 40 patients experienced a patellar redislocation within 24 months after the primary dislocation, whereas 21 patients, who were assessed after a median follow-up of 37 months (range 24–60 months), had not experienced a subsequent episode of lateral patellar instability. In all patients, age at the time of the primary dislocation, gender, the affected body side, body mass index, bilateral instability, physical activity according to Baecke’s questionnaire, the grade of trochlear dysplasia, patellar height, tibial tuberosity–trochlear groove (TT–TG) distance, and patellar tilt were assessed. The odds ratio (OR) of each factor with regard to the patellar redislocation was calculated using contingency tables. Based on these data, a “patellar instability severity score” was calculated.


The patellar instability severity score has six factors: age, bilateral instability, the severity of trochlear dysplasia, patella alta, TT–TG distance, and patellar tilt; the total possible score is seven. Reapplying this score to the study population revealed a median score of 4 points (range 2–7) for those patients with an early episode of patellar redislocation and a median score of 3 points (range 1–6) for those without a redislocation (p = 0.0004). The OR for recurrent dislocations was 4.88 (95 % CI 1.57–15.17) for the patients who scored 4 or more points when compared with the patients who scored 3 or fewer points (p = 0.0064).


Based on the individual patient data, the patellar instability severity score allows an initial risk assessment for experiencing a recurrent patellar dislocation and might help differentiate between responders and non-responders to conservative treatment after primary lateral patellar instability.

Level of evidence

Case–control study, Level III.


Patellar instability Patellar dislocation Redislocation Score 


Conflict of interest

The authors report no potential conflict of interest.


  1. 1.
    Arendt EA, Fithian DC, Cohen E (2002) Current concepts of lateral patella dislocation. Clin Sports Med 21:499–519PubMedCrossRefGoogle Scholar
  2. 2.
    Baecke JA, Burema J, Frijters JE (1982) A short questionnaire for the measurement of habitual physical activity in epidemiological studies. Am J Clin Nutr 36:936–942PubMedGoogle Scholar
  3. 3.
    Balcarek P, Jung K, Ammon J, Walde TA, Frosch S, Schüttrumpf JP, Stürmer KM, Frosch KH (2010) Anatomy of lateral patellar instability: trochlear dysplasia and tibial tubercle-trochlear groove distance is more pronounced in women who dislocate the patella. Am J Sports Med 38:2320–2327PubMedCrossRefGoogle Scholar
  4. 4.
    Balcarek P, Walde TA, Frosch S, Schüttrumpf JP, Wachowski MM, Stürmer KM, Frosch KH (2011) Patellar dislocations in children, adolescents and adults: a comparative MRI study of medial patellofemoral ligament injury patterns and trochlear groove anatomy. Eur J Radiol 79:415–420PubMedCrossRefGoogle Scholar
  5. 5.
    Buchner M, Baudendistel B, Sabo D, Schmitt H (2005) Acute traumatic primary patellar dislocation: long-term results comparing conservative and surgical treatment. Clin J Sports Med 15:62–66CrossRefGoogle Scholar
  6. 6.
    Cash JD, Hughston JC (1988) Treatment of acute patellar dislocation. Am J Sports Med 16:244–249PubMedCrossRefGoogle Scholar
  7. 7.
    Christiansen SE, Jakobsen BW, Lund B, Lind M (2008) Isolated repair of the medial patellofemoral ligament in primary dislocation of the patella: a prospective randomized study. Arthroscopy 24:881–887PubMedCrossRefGoogle Scholar
  8. 8.
    Dejour H, Walch G, Nove-Josserand L, Guier C (1994) Factors of patellar instability: an anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc 2:19–26PubMedCrossRefGoogle Scholar
  9. 9.
    Diederichs G, Köhlitz T, Kornaropoulos E, Heller MO, Vollnberg B, Scheffler S (2013) Magnetic resonance imaging analysis of rotational alignment in patients with patellar dislocations. Am J Sports Med 41:51–57PubMedCrossRefGoogle Scholar
  10. 10.
    Elias DA, White LM, Fithian DC (2002) Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella. Radiology 225:736–743PubMedCrossRefGoogle Scholar
  11. 11.
    Fithian DC, Paxton EW, Stone ML, Silva P, Davis DK, Elias DA, White LM (2004) Epidemiology and natural history of acute patellar dislocation. Am J Sports Med 32:1114–1121PubMedCrossRefGoogle Scholar
  12. 12.
    Fucentese SF, von Roll A, Koch PP, Epari DR, Fuchs B, Schöttle PB (2006) The patella morphology in trochlear dysplasia—a comparative MRI study. Knee 13:145–150PubMedCrossRefGoogle Scholar
  13. 13.
    Hiemstra LA, Kerslake S, Lafave M, Heard SM, Buchko GM (2013) Introduction of a classification system for patients with patellofemoral instability (WARPS and STAID). Knee Surg Sports Traumatol Arthrosc. doi: 10.1007/s00167-013-2477-0 PubMedGoogle Scholar
  14. 14.
    Hing CB, Smith TO, Donell S, Song F (2011) Surgical versus non-surgical interventions for treating patellar dislocation. Cochrane Database Syst Rev 9(11):CD008106Google Scholar
  15. 15.
    Insall J, Salvati E (1971) Patella position in the normal knee joint. Radiology 101:101–104PubMedCrossRefGoogle Scholar
  16. 16.
    Lippacher S, Dejour D, Elsharkawi M, Dornacher D, Ring C, Dreyhaupt J, Reichel H, Nelitz M (2012) Observer agreement on the Dejour trochlear dysplasia classification: a comparison of true lateral radiographs and axial magnetic resonance images. Am J Sports Med 40:837–843PubMedCrossRefGoogle Scholar
  17. 17.
    Nikku R, Nietosvaara Y, Aalto K, Kallio PE (2005) Operative treatment of primary patellar dislocation does not improve medium-term outcome: a 7-year follow-up report and risk analysis of 127 randomized patients. Acta Orthop 76:699–704PubMedCrossRefGoogle Scholar
  18. 18.
    Nikku R, Nietosvaara Y, Kallio PE, Aalto K, Michelsson JE (1997) Operative versus closed treatment of primary dislocation of the patella: similar 2-year results in 125 randomized patients. Acta Orthop Scan 68:419–423CrossRefGoogle Scholar
  19. 19.
    Nomura E (1999) Classification of lesions of the medial patellofemoral ligament in patellar dislocation. Int Orthop 23:260–263PubMedCrossRefPubMedCentralGoogle Scholar
  20. 20.
    Palmu S, Kallio PE, Donell ST, Helenius I, Nietosvaara Y (2008) Acute patellar dislocation in children and adolescents: a randomized clinical trial. J Bone Joint Surg Am 90:463–470PubMedCrossRefGoogle Scholar
  21. 21.
    Schöttle PB, Zanetti M, Seifert B, Pfirrmann CW, Fucentese SF, Romero J (2006) The tibial tuberosity–trochlear groove distance; a comparative study between CT and MRI scanning. Knee 13:26–31CrossRefGoogle Scholar
  22. 22.
    Senavongse W, Amis AA (2005) The effects of articular, retinacular or muscular deficiencies on patellofemoral joint stability: a biomechanical study in vitro. J Bone Joint Surg Br 87:577–582PubMedCrossRefGoogle Scholar
  23. 23.
    Senavongse W, Farahmand F, Jones J, Andersen H, Bull AM, Amis AA (2003) Quantitative measurement of patellofemoral joint stability: force–displacement behavior of the human patella in vitro. J Orthop Res 21:780–786PubMedCrossRefGoogle Scholar
  24. 24.
    Sillanpää PJ, Mäenpää HM, Mattila VM, Visuri T, Pihlajamäki H (2008) Arthroscopic surgery for primary traumatic patellar dislocation: a prospective, nonrandomized study comparing patients treated with and without acute arthroscopic stabilization with a median 7-year follow-up. Am J Sports Med 36:2301–2309PubMedCrossRefGoogle Scholar
  25. 25.
    Sillanpää PJ, Mattila VM, Mäenpää H, Kiuru M, Visuri T, Pihlajamäki H (2009) Treatment with and without initial stabilizing surgery for primary traumatic patellar dislocation. A prospective randomized study. J Bone Joint Surg Am 91:263–273PubMedCrossRefGoogle Scholar
  26. 26.
    Smith TO, Donell ST, Clark A, Chester R, Cross J, Kader DF, Arendt EA (2013) The development, validation and internal consistency of the Norwich Patellar Instability (NPI) score. Knee Surg Sports Traumatol Arthrosc. doi: 10.1007/s00167-012-2359-x Google Scholar
  27. 27.
    Stefancin JJ, Parker RD (2007) First-time traumatic patellar dislocation: a systematic review. Clin Orthop Relat Res 455:93–101PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Peter Balcarek
    • 1
    Email author
  • Swantje Oberthür
    • 1
  • Stephanie Hopfensitz
    • 1
  • Stephan Frosch
    • 1
  • Tim Alexander Walde
    • 1
  • Martin Michael Wachowski
    • 1
  • Jan Philipp Schüttrumpf
    • 1
  • Klaus Michael Stürmer
    • 1
  1. 1.Department of Trauma Surgery, Plastic and Reconstructive SurgeryUniversity Medical CentreGöttingenGermany

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