Patellar dislocation

Original Editors - Jeremy Luytens as part of the Vrije Universiteit Brussel's Evidence-based Practice project

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This article is currently under review and may not be up to date. Please come back soon to see the finished work! (5 May 2024)

Definition/Description[edit | edit source]

A patellar dislocation occurs by a lateral shift of the patella, leaving the trochlea groove of the femoral condyle.[1]

patella dislocation

Clinically relevant anatomy[edit | edit source]

The patellofemoral joint makes part of the knee joint. The articular surfaces consist of the patella and the trochlear surface of the femoral condyles. The articular cartilage on the medial facet is thicker than on the lateral facet, with the lateral facet bigger than the medial.[2] It has an anterior projection on the lateral femoral condyle, lateral to the patellar groove. This prevents lateral dislocation of the patella. [2][3] The patellofemoral articulation depends on the function of the quadriceps as it increases the angle of pull of the patellar tendon, improving the mechanical advantage of the quadriceps in knee extension.[4]


The suspension and movement of the patella is provided by passive and active stabilizers:[4]

  • Passive stabilizers: Tensor fascia lata, patellar ligament, knee capsule, patellofemoral ligament (medial and lateral), meniscopatellar ligament (medial and lateral)
  • Active: Quadriceps, patellar ligament, retinaculum

Epidemiology/Etiology[edit | edit source]

Epidemiology[edit | edit source]

The incidence for acute primary patellar dislocations are 2-3%.[5][6] Patellar disolocations are often associated with athletes[7][8], and is most common in females in the second decade of life.[9]

Etiology[edit | edit source]

Primary patellar dislocation is defined as traumatic disruption of the previously uninjured medial peripatellar structures.[5][6] It often results from a non-contact injury to the knee.

Predisposing factors include both morphological and functional patellofemoral disorders:[9][10][11]

  • Reduced osseous constraint form the lateral femoral condyle
  • Imbalance between stronger lateral tissues (e.g. lateral retinaculum and vastus lateralis), which are able to overcome weaker medial structures, especially the medial patellofemoral ligament and the distal vastus medialis
  • Biomechanical issues such as femoral and tibial rotation, and pes planus
  • Patella alta
  • Genu recurvatum
  • Icreased Q-Angle
  • Patellar hypermobility

Mechanism of injury[edit | edit source]

  • Non-contract: Twisting of the leg, with internal rotation of the femur on a fixed foot and tibia
    • Often associated with valgus stress (strong lateral force then dislocates the patella)[8]
  • Traumatic: A direct blow to the knee (lateral or medial)[10]

Clinical presentation[edit | edit source]

One of the common findings related to acute, primary, traumatic patellar dislocations is hemarthrosis of the knee, caused by rupture of the medial restraints of the patella.[12] Medial swelling will also be prominent.[9]

Main complaints from the patient will include:[9]

  • Pain
  • Instability of the knee
  • Locking of the knee after the trauma

Differential diagnosis[edit | edit source]

[9][11]

Diagnostic procedures[edit | edit source]

  • X-rays; To exclude associated fractures (osteochondral, avulsion); sublaxation will be seen on lateral view
  • CT: To measure tuberosity tibia-trochlea groove distance
  • MRI: To differentiate degree of tear

[13]

Outcome measures[edit | edit source]

[14]

Physical examination[edit | edit source]

  • Observation:
  • Measure Q-Angle
  • Special tests:[9][11]
    • Patella apprehension test
    • Patella tracking assessment
    • Patellar hypermobility

Medical management[edit | edit source]

Acute[edit | edit source]

  • Immobilization for 6 weeks (cylinder cast/back slab/knee range of motion brace)[15] OR
  • Surgical management via arthroscopy:[10][16]
    • With or without surgical repair of the torn retinacullum or immediate patellar realignment
  • Medication:
    • Supplements like glucosamine and
    • NSAID’s

Surgical management[edit | edit source]

Indications:[17][18]

  • Recurrent/chronic dislocation
  • Patellofemoral symptoms

Other than preferences for nonoperative treatment of primary patellar dislocations have been shown in previous studies [20,21,22], patients with habitual dislocations and patellofemoral symptoms seem to be benefited from reconstructive surgery [23,24]. High-level evidence supports nonoperative treatment for first-time lateral acute patellar dislocations. Surgical intervention is often indicated for recurrent dislocations [43]. However, according to studies [46] (Level of evidence: 3a), surgical treatment is associated with a higher risk of patellofemoral joint osteoarthritis. Therefore, it is of major importance to formulate one's management strategy patient oriented and to inform patients of the advantages and disadvantages of each management strategy when deciding.

Physiotherapy management[edit | edit source]

Conservative management[edit | edit source]

Goals:

  • Improve function
  • Prevent further dislocation:
    • Taping: Lateral reinforcement will reduce the movement of the patella (to prevent dislocation)[9]

Physiotherapy modalities include:[9][10][19]

  • Prevention of re-dislocation:
    • Taping: Lateral reinforcement will reduce the movement of the patella (to prevent dislocation)[9]
    • Bracing
    • Reassurance and behavioural modification[20]
  • Improve range of motion:
  • Combination therapy
  • Strengthening exercises:
    • Quadriceps[21], hamstrings, adductors, hip and lower abdomen
    • Closed kinetic chain exercises are recommended
  • Stretching:
    • Improve flexibility of hamstrings and quadriceps
  • Proprioception: Improve stability of the knee


Other than preferences for nonoperative treatment of primary patellar dislocations have been shown in previous studies [20,21,22], patients with habitual dislocations and patellofemoral symptoms seem to be benefited from reconstructive surgery [23,24]. High-level evidence supports nonoperative treatment for first-time lateral acute patellar dislocations. Surgical intervention is often indicated for recurrent dislocations [43]. However, according to studies [46] (Level of evidence: 3a), surgical treatment is associated with a higher risk of patellofemoral joint osteoarthritis. Therefore, it is of major importance to formulate one's management strategy patient oriented and to inform patients of the advantages and disadvantages of each management strategy when deciding.

Non-operative treatment:

Conservative treatment is still the most common treatment after primary dislocation of the patella. [25]
There is no statistically significant difference (p=0.091) between operatively and conservatively treated groups with regard to functional results. The same statistical outcome emerged when comparing incidences of re-dislocation (p=0.854), or other major patellar instabilities (p=0.856), between the groups. [26].
The results obtained should not promote a non-operative method on the basis of lower risk, but do support an individual approach based on precise diagnosis and defined criteria. [26].

Thus it appears that surgical and nonsurgical management of patellar dislocation tends to yield similar results in the skeletally mature and adolescents. Individual characteristics and goals should be taken into consideration when choosing an acute patellar dislocation treatment approach. Unless future studies show a more definitive benefit for surgical management, exercise and bracing should be considered initially. Exercise and bracing are less invasive and likely to be less expensive than surgery. [41]

Surgeon experience as well as individual patient values and preferences should primarily guide management. [42]

Studies have shown taping resulted in a significantly better Lysholm score at 6 and 12 weeks post-dislocation (P=0.05), and also after 5-year follow-up (P=0.01). Knee function was better at 1-year follow-up. There were no cases of recurrent dislocation. [27]. 1B

Tape bandage immobilization seems superior to a cylinder cast even after 5 years. [27].

Contemporary treatment regimens range from immediate mobilization without a brace to cast immobilization in extension for 6 weeks. In a patient who finds 6 weeks of immobilization unacceptable, a 3-week period of immobilization may be performed with the understanding that a higher redislocation rate may result. A 3-fold higher risk of redislocation was reported in those treated with immediate mobilization. [40]
Surgical treatment:

Surgical intervention for first-time traumatic patellar dislocation is indicated in the following situations:
1) evidence on imaging or clinical examination of osteochondral fracture or major chondral injury;
2) palpable or MRI findings of substantial disruption of the MPFL (medial patellofemoral ligament)-VMO (vastus medialis obliquus)-adductor mechanism;
3) a patella laterally subluxated on the plain Mercer-Merchant view with normal alignment on the contralateral knee;
4) a patient fails to improve with nonoperative management especially in the presence of one or more predisposing factors to patellar dislocation;
5) subsequent redislocation [28]. Surgical stabilization significantly reduced the redislocation rate of primary traumatic patellar dislocation in a young adult population than those without surgical treatment, which was addressed in a prospective, randomized, controlled study [29].


For surgical treatment, There are several surgical options that may be used to prevent patellar dislocation and subluxation. These procedures may be used alone or in a combination:
- Lateral release
- Medial patellofemoral ligament (MPFL) reconstruction / proximal realignment
- Distal realignment / anteromedialization (AMZ)

Lateral release

Release of tight lateral retinaculum (soft tissue) to allow patella to track more medially. This procedure is sometimes performed alone on patients with mild instability of the patella.

Medial patellofemoral ligament (MPFL) reconstruction

A tightening of the MPFL or a reconstruction of this ligament can be used to balance the tracking of the patella to more natural (medial) alignment. This procedure is performed in patients with more severe patellar instability. A lateral release often is performed in conjunction with this procedure. (38)
After research 93% had good/exellent results using the Fulkerson’s functional knee score: Radiographic evaluation showed significant improvements in the congruence angle by an average of 20° (P= .0006), and in the lateral patellofemoral angle by an average of 10° (P = .0003). [32]

Conclusion: initial acute patellofemoral dislocations should be treated with immobilization and rehabilitation, as a majority of patients will do well without surgery. MRI is necessary to assess for osteochondral lesions, because they are associated with a poor prognosis if they are not addressed.

Distal realignment / anteromedialization (AMZ)

This realignment procedure involves transferring the tibial tubercle (where the patellar tendon attaches to the tibia). The bony attachment of the tendon is moved more medially to allow the patella to track normally. This procedure is performed on patients with severe patellar instability and is used in conjunction with the lateral release and/or the MPFL reconstruction.

Following the operation you will be taken to the recovery room for observation. Once the effects of the anesthesia have worn off and your pain is under control you will be released. Initial treatment after surgery consists of pain management, physical therapy and cryotherapy (ice). (38)

Resources[edit | edit source]

Clinical Bottom Line[edit | edit source]

References[edit | edit source]

  1. ↑ Frobell R, Cooper R, Morris H, Arendt, H. Acute knee injuries. In: Brukner P, Bahr R, Blair S, Cook J, Crossley K, McConnell J, McCrory P, Noakes T, Khan K. Clinical Sports Medicine: 4th edition. Sydney: McGraw-Hill. p.626-683.
  2. ↑ 2.0 2.1 Matthijs O, Van Paridon-Edauw D, Winkel D. Hoofdstuk 2 knie. Manuele therapie van de perifere gewrichten. 1e uitgave. Houten. Bohn Stafleu Van Loghum bv. 2004. pp.220–235.
  3. ↑ Bijl GVD (Jr), De Graaf CG, De Ridder PA. In: Actief en passief bewegen in de gewrichten der extremiteiten. De tijdsstroom, 1975. p.126.
  4. ↑ 4.0 4.1 Egmond DL, Schuitemaker R. De knieregio. In: Mink AJF, Rer Veer HJ, Vorselaars JACTh. Extremiteiten manuele therapie in enge en ruime zin. 1e uitgave. Houten. Bohn Stafleu Van Loghum bv, 2006. p.559–628.
  5. ↑ 5.0 5.1 Atkin DM, Fithian DC, Marangi KS, Stone ML, Dobson BE, Mendelsohn C. Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury. Am J Sports Med 2000;28:472–479.
  6. ↑ 6.0 6.1 Kirsch MD, Fitzgerald SW, Friedman H, Rogers LF. Transient lateral patellar dislocation: diagnosis with MR imaging. AJR Am J Roentgenol 1993;161:109–113.
  7. ↑ Ficat RP, Hungerford DS. Disorders of the patello-femoral joint. Williams & Wilkins, 1977.
  8. ↑ 8.0 8.1 Hughston JC, Walsh WM, Puddu G. Patellar subluxation and dislocation. WB Saunders Company, 1984.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 Meeusen R. Praktijkgids knieletsels. Cursus. Vrije Universiteit Brussel, 2011.
  10. ↑ 10.0 10.1 10.2 10.3 Skinner HB, Barrack RL, Bedmar MS, Clarson GD. Sports medicine. In: Reinhardt S, Nogueira I, Boyle PJ. Current diagnosis en treatment in orthopedics. 2nd edition. McGraw-Hill: United States of America, 2000. p.125–175.
  11. ↑ 11.0 11.1 11.2 Beeton KS. The knee. Manual therapy masterclass: the peripheral joints. Churchill Livingstone. Elsevier, 2003. p.54–55.
  12. ↑ Tsai CH, Hsu CJ, Hung CH, Hsu HC. Primary traumatic patellar dislocation. Journal of orthopaedic surgery and research 2012;7(1):21.
  13. ↑ Hohlweck J, Quack V, Arbab D, Spreckelsen C, Tingart M, Lüring C, Rath B. Diagnostic and therapeutic management of primary and recurrent patellar dislocations-analysis of a nationwide survey and the current literature. Zeitschrift für Orthopädie und Unfallchirurgie, 201;151(4):380-8.
  14. ↑ Paxton EW, Fithian DC, Lou Stone M, Silva P. The reliability and validity of knee-specific and general health instruments in assessing acute patellar dislocation outcomes. The American journal of sports medicine, 2003;31(4):487-92.
  15. ↑ Van Gemert JP, de Vree LM, Hessels RA, Gaakeer MI. Patellar dislocation: cylinder cast, splint or brace? An evidence-based review of the literature. International journal of emergency medicine, 2012;5(1):45.
  16. ↑ Castelyn P. Acute knee injuries, diagnostic and treatment managment proposals. Vub University press, 2001. p.42-43.
  17. ↑ Fithian DC, Paxton EW, Cohen AB. Indications in the treatment of patellar instability. The journal of knee surgery, 2004;17(01):47-56.
  18. ↑ Koskinen SK, Rantanen JP, Nelimarkka OI, Kujala UM. Effect of Elmslie-Trillat and Roux-Goldthwait procedures on patellofemoral relationships and symptoms in patients with patellar dislocations. The American journal of knee surgery, 1998;11(3):167-73.
  19. ↑ Smith TO, Davies ., Chester R, Clark A, Donell ST. Clinical outcomes of rehabilitation for patients following lateral patellar dislocation: a systematic review. Physiotherapy, 2010;96(4):269-81.
  20. ↑ Smith TO, Chester R, Clark A, Donell ST, Stephenson R. A national survey of the physiotherapy management of patients following first-time patellar dislocation. Physiotherapy, 2011;97(4):327-38.
  21. ↑ Smith TO, Chester R, Cross J, Hunt N, Clark A, Donell ST. Rehabilitation following first-time patellar dislocation: a randomised controlled trial of purported vastus medialis obliquus muscle versus general quadriceps strengthening exercises. The Knee,2015;22(4):313-20.

13) Journal of otrhopaedic surgery and research.Primary traumatic patellar dislocation. Chun-Hao Tsai. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3511801
14) Atkin DM, Fithian DC, Marangi KS, Stone ML, Dobson BE, Mendelsohn C. Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury. Am J Sports Med. 2000;28:472–479. [PubMed]
15) Atkin DM, Fithian DC, Marangi KS, Stone ML, Dobson BE, Mendelsohn C. Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury. Am J Sports Med. 2000;28:472–479. [PubMed]
16) Kirsch MD, Fitzgerald SW, Friedman H, Rogers LF. Transient lateral patellar dislocation: diagnosis with MR imaging. AJR Am J Roentgenol. 1993;161:109–113. [PubMed]
17) http://www.physio-pedia.com/Quadriceps_tendon_tear/Differential diagnosis
18) Hohlweck J., Diagnostic and therapeutic management of primary and recurrent patellar dislocations - analysis of a nationwide survey and the current literature. Zeitschrift für Orthopädie und Unfallchirurgie. 2013 Aug;151(4):380-8. [Pubmed]
19) Picture from: www.slideshare.net/bhavinj/mri-of-patellar-disorders (Bhavin Jankharia, Doctor at Jankharia Imaging, Mumbai, India)
20) Nikku R, Nietosvaara Y, Aalto K, Kallio PE. 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. 2005;76:699–704. doi: 10.1080/17453670510041790. [PubMed] [Cross Ref] (level of evidence 1B)
21) Arendt EA, Fithian DC, Cohen E. Current concepts of lateral patella dislocation. Clin Sports Med. 2002;21:499–519. doi: 10.1016/S0278-5919(02)00031-5. [PubMed] [Cross Ref] (level of evidence 2C)
22) Buchner M, Baudendistel B, Sabo D, Schmitt H. Acute traumatic primary patellar dislocation: long-term results comparing conservative and surgical treatment. Clin J Sport Med. 2005;15:62–66. doi: 10.1097/01.jsm.0000157315.10756.14. [PubMed] [Cross Ref]
(level of evidence 2B)
23) Fithian DC, Paxton EW, Cohen AB. Indications in the treatment of patellar instability. J Knee Surg. 2004;17:47–56. [PubMed] (level of evidence 2C)
24) Koskinen SK, Rantanen JP, Nelimarkka OI, Kujala UM. Effect of Elmslie-Trillat and Roux-Goldthwait procedures on patellofemoral relationships and symptoms in patients with patellar dislocations. Am J Knee Surg. 1998;11:167–173. [PubMed] (level of evidence 1C)
25) Hohlweck J., Diagnostic and therapeutic management of primary and recurrent patellar dislocations - analysis of a nationwide survey and the current literature. Zeitschrift für Orthopädie und Unfallchirurgie. 2013 Aug;151(4):380-8. [Pubmed] (level of evidence 4)
26) Apostolovic M., Vukomanovic B., Slavkovic N., Vuckovic V., Vukcevic M., Djuricic G., and Kocev N., Acute patellar dislocation in adolescents: operative versus nonoperative treatment. Int Orthop. 2011 Oct [PubMed] (level of evidence 2B)
27) Akkie Rood, Harm Boons, Joris Ploegmakers, William van der Stappen, Sander Koëter; Tape versus cast for non-operative treatment of primary patellar dislocation: a randomized controlled trial; Archives of Orthopaedic and Trauma Surgery; 2012 [PubMed] (level of evidence 1B)
28) Stefancin JJ, Parker RD. First-time traumatic patellar dislocation: a systematic review. Clin Orthop Relat Res. 2007;455:93–101. [PubMed]
(level of evidence 3A)
29) Sillanpaa PJ, Mattila VM, Maenpaa H, Kiuru M, Visuri T, Pihlajamaki H. Treatment with and without initial stabilizing surgery for primary traumatic patellar dislocation. A prospective randomized study. J Bone Joint Surg Am. 2009;91:263–273. doi: 10.2106/JBJS.G.01449. [PubMed] [Cross Ref] (level of evidence 1B)
30) van Gemert et al.. Patellar dislocation: cylinder cast, splint or brace? An evidence-based review of the literature. International Journal of Emergency Medicine 2012 5.45
31) White BJ et al. Patellofemoral instability: bulletin of the NYU Hospital for Joint Diseases 2009; 67
32) David Drez, T.Bradley Edwards; Claude S. Williams: Results of medial patellofemoral ligament reconstruction in the treatment of patellar dislocation ; March 2001; Arthroscopy: The Journal of Arthroscopic and Related Surgery (level of evidence 4)
33) Peter R.Miller, Roger M.Klein. Robert A. Teitge : Medial dislocation of the patella; August 1991, Volume 20; Issue 6; pp 429-431
34) Elizabeth W. Paxton, Donald C. Fithian, Mary Lou Stone and Patricia Silva: The Reliability and Validity of Knee-Specific and General Health Instruments in Assessing Acute Patellar Dislocation Outcomes; July 2003
35) Mizuno, Y., Kumagai, M., Mattessich, S. M., Elias, J. J., Ramrattan, N., Cosgarea, A. J. and Chao, E. Y. S. (2001), Q-angle influences tibiofemoral and patellofemoral kinematics. J. Orthop. Res., 19: 834–840. doi: 10.1016/S0736-0266(01)00008-0
36) Smith TO, The reliability and validity of the Q-angle: a systematic review , Knee Surg Sports Traumatol Arthrosc. 2008 Dec;16(12):1068-79. doi: 10.1007/s00167-008-0643-6. Epub 2008 Oct 8.
37) Emami MJ, Q-angle: an invaluable parameter for evaluation of anterior knee pain, Arch Iran Med. 2007 Jan;10(1):24-6.
38) http://ukhealthcare.uky.edu/uploadedFiles/UKHC-SportsMed-Medial-Patellofemoral-Lig-Recon.pdf
39) Chris S et al; Femoral Neuropathy due to patellar dislocation in a theatical and jazz dancer: a case report; Arch Phys Med Rehabil Vol 86, June 2005.
40 Neel P. Jain, MD, Najeeb Khan, MD, and Donald C. Fithian, MD; A Treatment Algorithm for Primary Patellar Dislocations ; Sports Health. 2011 March

41) Fuller J., Hammil H., Prochinske K., Druall C., “Operative vs. Nonoperative Treatment after Acute Patellar Dislocation: Which is more Effective at Reducing Recurrence in Adolescents?”. Journal of Sport Rehabilitation, © 2017 Human Kinetics, Inc. [PubMed] (level of evidence 1A)

42) Khan M. and Miller B., Cochrane in CORR®: Surgical Versus Non-surgical Interventions for Treating Patellar Dislocation (Review). Clin Orthop Relat Res. 2016 Nov [Pubmed] (level of evidence 1A)
43) Weber A.E., Nathani A., Dines J.S., Allen A.A., Shuyin-Stein B.E., Arendt E.A., Bedi A., "An algorithmic Approach to the Management of Recurrent Lateral Patellar Dislocation." (review). J Bone Joint Surg Am. 2016 Mar [Pubmed] (level of evidence 1A)

44) Smith T., Cheste R., Cross J., Hunt N., Clark a., Donnel S., Rehabilitation following first-time patellar dislocation: a randomised controlled trial of purported vastus medialis obliquus muscle versus general quadriceps strengthening exercises. 2015 Elsevier. [Pubmed] (level of evidence 1B)

45) SMITH (Toby O.), CHESTER (Rachel), CLARK (Allan), DONELL (Simon T.), STEPHENSON (Richard). A national survey of the physiotherapy management of patients following first-time patellar dislocation, in Physiotherapy, 2011, vol. 97, nr. 4, p. 327–338. [Online] http://www.sciencedirect.com.myezproxy.vub.ac.be/science/article/pii/S0031940611000265?via%3Dihub (Level of evidence: 2b)

46) SMITH (Toby O.), SONG (Fujian), DONELL (Simon T.), HING (Caroline B.). Operative versus non-operative management of patellar dislocation. A meta-analysis, in Knee Surgery, Sports Tramatology, Arthroscopy, 2011, vol. 19, nr. 6, p. 988-998. [Online] https://link-springer-com.myezproxy.vub.ac.be/article/10.1007%2Fs00167-010-1355-2 (Level of evidence: 3a)

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