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Patellar Fractures


Patella fractures result from direct trauma or stress, or they are the indirect result of overstressing the quadriceps contraction or extensor mechanisms. [1][2][3] Collateral injuries are usually associated with tears of the retinaculum and quadriceps muscle. [1] Supplement for Patella Fracture It accounts for approximately 1% of all skeletal injuries and occurs in all age groups. [4][5][6]

Clinically relevant anatomy

The patella is a triangular-shaped bone located on the anterior surface of the knee joint distal to the femur. It is the largest sesamoid bone in the body and is part of the knee joint. [7][8][9] The main function of the patella is to act as a fulcrum to increase the moment arm of the knee joint. Broad capabilities of the quadriceps and knee joints. [10]

The vastus medialis and vastus lateralis control the movement of the patella as part of the quadriceps group. [11] The medial retinaculum formed by the vastus medialis and quadriceps aponeurosis and the lateral retinaculum formed by the vastus lateralis and iliotibial band both contribute to knee extension. [6]

The entire extensor mechanism plays an important role in patellar fractures. The extensor mechanism consists of the quadriceps tendon retinaculum with the patellar tendon tibial tuberosity and the patellofemoral and patellotibial ligaments [12]. See the Patella page for more details on the anatomy.


A 2016 study found that the incidence of patellar fractures was 13.1/100,000 per year, and the incidence increased with age [13]. Women account for 56% of patellar fractures and men account for 44% of patellar fractures. [13] A more recent Swedish study also found that older (>65 years old) Women had a higher percentage (64%) of patella fractures compared to men. [14] Most fractures are caused by low-energy trauma, 70% of which are due to simple falls, especially in winter. [14]

Patella fractures were not associated with increased mortality, as the relative risk of death was 0.9. [15] In a recent study, the average one-year mortality rate after patellar fracture increased from 2.8% to 6.2% in the elderly population.

  • Injury (sprain/rupture) to the ligaments and tendons that attach to the patella
  • Avascular necrosis[16]
  • Post-traumatic arthritis
  • Patellofemoral Osteochondral Injury
  • Stiffness
  • Non-union
  • Malunion
  • Concomitant injuries (eg, acetabular, femoral and tibial injuries)
  • Long term complications:[17]
    • Stiffness
    • Extension weakness
    • Patellofemoral arthritis.


Characteristics/Clinical Presentation

Types of fractures

Patella fractures are divided into displaced and non-displaced types. Displaced fractures are unstable and can be further classified as: [18]

  • Crush: due to direct trauma (mainly due to a blow or fall with the knee bent)
    • Can cause damage to the articular cartilage of the patella and femoral condyles.
  • Lateral/Stellate: due to muscle contraction/extensive stress on the extensor mechanism, e.g. explosive contraction of the quadriceps after a jump from a height.
    • Most common type[13]
    • Proximal blood supply may be compromised
    • Usually the result of excessive knee flexion
  • Edge: due to knee fall
  • Vertical/longitudinal
  • Lower/upper pole
  • Osteochondral
  • Sleeve (only in paediatric patients)


The prognosis of an injury depends on the degree of cartilage damage at the time of the injury. Functional outcome depends on the ability to achieve pain-free and stable range of motion in the early stages. [20]

Differential diagnosis
  • Bipartite patella[1]
  • Knee dislocation
  • Patella dislocation


  • Details regarding accident
  • Mechanism of injury
  • Pain at knee
  • Complaints of difficulty standing or a popping sensation in the knee


Physical examination
  • Observation:
    • Whole extremity
    • Swollen, bruised knee
    • Deformity around knee
    • Possible wounds (open fracture)
  • Palpation (usually done under local anesthesia to relieve pain):
    • Tenderness around patella
    • Palpable gap (for displaced fractures)
  • Rule out concomitant injuries:
    • eg acetabular femoral and tibial fractures
  • Haemarthrosis
  • Range of motion:
    • Acute:
      • Knee limitation and knee flexion and extension pain
      • Often unable to do straight leg raise
    • Chronic:
      • Full knee flexion with extension lag
  • Distal pulses
  • Assess compartment of the leg
  • Neurological assessment


Special investigations


  • AP view:
    • May be difficult to see patella
  • Lateral view:
    • Undisplaced – < 2mm separation
    • Displacement -> 2mm separation step deformity
  • Sky view
  • For regular monitoring of the healing process and any possible complications
AP viewLateral view
  • CT scan: Usually not needed
  • MRI: Diagnosis of nearby tendon and ligament-related injuries
  • Bone scans: To identify stress fractures

Outcome measures

  • Knee Injury and Osteoarthritis Outcome Score
  • Knee outcome survey
  • Lower extremity function scale
  • McGill pain questionnaire
Medical management
  • In acute cases, a local anesthetic may be given to relieve pain. [21] This aids in the evaluation and diagnosis of patellar fractures.
Conservative management

Indications: Nondisplaced fractures (mainly vertical horizontal and comminuted fractures) with extensor mechanisms in place [1][20]


  • Fracture Immobilization with POP Cylinder Cast or Locked Range of Motion Brace in Extension (4-6 weeks):
    • Knee flexion can be gradually increased as healing occurs
    • Range of motion brace must be worn until healing (on x-ray) and clinical signs of healing (no tenderness to palpation)
  • Crutch walking 6-8 weeks
  • Rehabilitation to restore full range of motion strength and restore function
Surgical intervention

Indications: Significant displacement of incomplete extensor mechanism[1] or joint stride >2-3 mm or fracture displacement >1-4 mm. [6]

Purpose: To restore extensor function to align joint incoordination and allow early movement [20][23][26][27]


  • Transverse/simple comminuted mid-patellar fractures: Open reduction and internal fixation using the tension band wire technique using needles and wire and a “figure of eight” to compress the fragments together
    • POP cast in extension for 6 weeks
Tension band wire ORIF
  • near end/far end
    • POP cast for 6 weeks
  • Longitudinal (uncommon): Interfracture screw fixation
  • For comminuted fractures/irreducible or irreparable fractures or severe cartilage damage: partial versus total patellar resection: [21]
    • The quadriceps attaches to the patellar tendon to ensure the function of the extensor apparatus during a complete patella resection [21]
    • Patella resection: relatively old procedure of last resort due to significant loss of extension
  • Repair of bilateral vastus muscles
  • Rehabilitation is the same as conservative treatment

Later stages:

When joint fibrosis occurs, it is necessary to operate under anesthesia or to release adhesions under arthroscopy. [20]

Physiotherapy management

Since clinical healing stages do not always correlate with theoretical healing, the surgeon will guide rehabilitation while taking into account the X-ray findings. The following are guidelines for the rehabilitation of patients after a patella fracture, but it is always good to discuss treatment Plan with referral to a plastic surgeon.

Conservative management

Conservative treatment is used when the extensor mechanism is still intact. [1]

Phase 1: 0-6 weeks

  • Range of motion (as per surgeon):
    • Range of motion brace locked in for 2-3 weeks of extension
    • Controlled motion brace at 2-3 weeks
    • Exercises:
      • Open kinetic chain strengthening and knee range of motion at 3-4 weeks – focusing on active flexion and extension in the inner range
      • Quadriceps
      • Hamstring
      • Gluts sets
      • SLR
      • Open and Closed Kinetic Chain Hip Strengthening Exercises
      • Circulatory drills
  • Weight-bearing:
    • Partial weight-bearing in brace
    • May stand tandem
    • Weight bearing restrictions are usually applied for 6-8 weeks[12][25]
    • Duration of crutches/weight bearing restrictions according to surgeon
  • Patella mobilization
  • Using Cryotherapy for Pain and Edema


Phase II: 6-12 weeks
  • Knee Support Range of Motion According to Surgeon
  • Range of motion:
    • Progress to full knee flexion and extension
  • Exercises:
    • Stationary bike with raised seat and no resistance
    • Progressive Closed Kinetic Chain Exercises: Mini Squats Strengthen Retro Steps and More
    • Progress resistance on hip exercises
    • Proprioception
    • Lunges from weeks 8-10


Post-operative rehabilitation

Surgical intervention is performed in cases where there is significant displacement and the extensor mechanism is incomplete. Open reduction and internal fixation using the tension band wire technique is usually the treatment of choice. [1]

Phase I: 0-2 weeks

  • Range of motion brace:
    • Lockdown extension (if not using POP conversion)
    • Take off during physical therapy only Allows 0-30° knee flexion range initially.
  • Mobilization:
    • Knee locked in extension
  • Exercises:
    • Isometric Quadriceps/Hamstrings/Adductors/Abductors Strengthening
    • Resistance to ankle movement (eg using a theraband)

Phase II: 2-6 weeks

  • Range of motion brace (if applicable):
    • Weight-bearing activities for locked-in stretches
    • May be removed at night
  • Range of motion:
    • Can increase flexion by 5° per week, reaching 90° by week 6
  • Exercises:
    • Isometric Quadriceps/Hamstrings/Adductors/Abductors Strengthening
    • Resistance to ankle movement (eg using a theraband)
    • Initiate SLR

Phase III: 6-10 weeks

  • Range of motion brace:
    • unlocked; for weight bearing activities
  • Range of motion:
    • Progress to full range of motion by week 10
  • Exercises: As previous phase

Phase IV: 10-12 weeks

  • Range of motion brace: Discontinue
  • Range of motion: Full
  • Exercises: As previous phase
    • Start with stationary cycling

Phase V: Up to 3-6 months

Resume normal activities as tolerable.


  1. ↑ Jump up to:1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 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. 2012; 626-683.
  2. ↑ Jump up to:2.0 2.1 Schuett D., Hake M., Mauffrey C., Hammerberg E., Stahel P., Hak D. Current treatment strategies for patella fractures. Orthopedics. 2015;38(6):377-84.
  3. ↑ Jump up to:3.0 3.1 Archdeacon M., Sanders R. Chapter 54 – Patella Fractures and Extensor Mechanism Injuries. In: Browner B.D., Jupiter J.B., Krettek C., Anderson P.A., (eds). Skeletal Trauma, 4th edition. Elsevier Health Sciences, 2008.
  4.  Crowther M., Mandal A., Sarangi P. Propagation of stress fracture of the patella. British journal of sports medicine 2005;39(2):e6.
  5.  Sweetnam R. Patellectomy. Postgraduate medical journal 1964 Sep;40(467):531.
  6. ↑ Jump up to:6.0 6.1 6.2 Posner A., Zimmerman J. Surgical management of patella fractures: a review. Archives of Orthopaedics 2022; 3(1):17-21.
  7.  Cedars-Sinai. Fractured Kneecap. Cedars Sinai organisation. https://www.cedars-sinai.org/health-library/diseases-and-conditions/f/fractured-kneecap.html (accessed 25/07/2018).
  8.  Schunke M. Anatomische atlas Prometheus, algemene anatomie en bewegingsapparaat. Bohn Stafieu van Loghum: 2e druk. 2010.
  9.  Everett L. Knee and Lower Leg. In: Marx J, Walls R, Hockberger R, editors. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 6th ed. Philadelphia: Mosby Elsevier, 2006.
  10. ↑ Jump up to:10.0 10.1 Melvin S.J., Mehta S. Patellar fractures in adults. Journal of the American Academy of Orthopaedic Surgeons 2011;19(4):198-207.
  11.  Orthopaedia. Collaborative Orthopaedic Knowledgebase, http://www.orthopaedia.com/display/Main/Patella+fractures (accessed November 10, 2010).
  12. ↑ Jump up to:12.0 12.1 12.2 12.3 Duke Orthopaedics. Wheeless’ textbook of Orthopaedics. Fractures of the patella.http://www.wheelessonline.com/ortho/fractures_of_the_patella (accessed November 10 2010).
  13. ↑ Jump up to:13.0 13.1 13.2 Larsen P., Court-Brown C., Vedel J., Vistrup S., Elsoe R. Incidence and Epidemiology of Patellar Fractures. Orthopedics; 2016 Nov 1;39(6):e1154-e1158.
  14. ↑ Jump up to:14.0 14.1 Kruse M., Wolf O., Mukka S., Bruggemann A. Epidemiology, classification and treatment of patella fractures: an observational study of 3194 fractures from the Swedish Fracture Register. Eur J Trauma Emerg Surg 2022; https://doi.org/10.1007/s00068-022-01993-0
  15.  Larsen P., Elsoe R. Patella fractures are not associated with an increased risk of mortality in elderly patients. Injury 2018; 49(10):1901-1904.
  16. ↑ Jump up to:16.0 16.1 Medscape. Patella Fracture Imaging. http://emedicine.medscape.com/article/394270-overview&gt (accessed 25/07/2018).
  17.  Insall JN. Fractured kneecap: treatments. Institute for Orthopaedics and sports medicine 2007.
  18. ↑ Jump up to:18.0 18.1 Whittle P. Fractures of the Lower Extremity. In: Canale S., Beaty J., (eds). Campbell’s Operative Orthopaedics. 11th ed. Philadelphia: Mosby Elsevier, 2008.
  19. ↑ Jump up to:19.0 19.1 19.2 19.3 19.4 Walters J. (ed). Orthopaedics – A guide for practitioners. 4th Edition. Cape Town: University of Cape Town, 2010.
  20. ↑ Jump up to:20.0 20.1 20.2 20.3 20.4 Mehling I., Mehling A., Rommens P. Comminuted patellar fractures. Current Orthopaedics 2006;20(6):397-404.
  21. ↑ Jump up to:21.0 21.1 21.2 21.3 21.4 Günal I., Karatosun V. Patellectomy: an overview with reconstructive procedures. Clinical Orthopaedics and Related Research 2001;389:74-8.
  22. ↑ Jump up to:22.0 22.1 McRae R., Esser M. Practical fracture treatment E-book. Churchill Livingstone/ Elsevier; 2002.
  23. ↑ Jump up to:23.0 23.1 23.2 Fourati MK. Reeducation du genou après fracture de la rotule. Ann. Kinésitherapie 1986.
  24.  Scolaro J., Bernstein J., Ahn J. In brief: patellar fractures. 2011;1213-1215.
  25. ↑ Jump up to:25.0 25.1 American Academy of Orthopaedic Surgeons. Diseases and conditions – Patellar (Kneecap) Fractures. http://orthoinfo.aaos.org/topic.cfm?topic=A00523 (accessed November 10 2010).
  26.  Shang ZG. Patellar fractures treatment and management. Unbound medline 2013;26(6):445-8.
  27. ↑ Jump up to:27.0 27.1 27.2 Strauss J. ORIF Patella Fracture Post-Operative Rehabilitation Protocol, Hospital for Joint Diseases, 2008.

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