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Patellar Pole Avulsion Fracture

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Other Names

  • Patellar Sleeve Fracture
  • Patellar Sleeve Avulsion Fracture
  • Patellar Sleeve Avulsion (PSA)
  • Pediatric Patellar Avulsion Fracture
  • Sleeve fracture of the patella


  • This page refers to patellar pole avulsion or sleeve fractures
    • Defined as an avulsion of the chondral or osteochondral "sleeve" from the inferior pole of the Patella
    • Very rarely, this can occur on the superior pole
  • This should not be confused with Patellar Apophysitis (Sinding-Larsen-Johansson Syndrome)
    • Although occurring along the inferior patellar pole, it is a chronic overuse injury



  • Demographics (need citation)
    • Occur in pediatrics between age 8 and 16
    • Mean age is 12.7 years
    • Occurs in males at a ratio of 3:1[1]
  • Represent less than 1% of all pediatric fractures[2]
  • Represents between 42% and 72% of patella fractures in children[3]


Illustration of patella sleeve avulsion fracture[4]
  • Patellar sleeve fracture
    • Defined as avulsion of a small fragment of bone and/or periosteum, retinaculum, and cartilage
    • Typically occurs at the inferior pole of the patella (rarely at the superior pole)
    • Articular cartilage is pulled from the deep side, periosteum and cartilage from the superficial side[5]
  • Patella is hypermobile
    • More susceptible due to rapid growth, increased sports activity, and relative patella instability
    • High cartilage-bone ratio at transformation zone
    • Increases vulnerability to acute, chronic eccentric loads and shearing forces
  • Mechanism (most common)
    • Indirect, acute forceful muscle contraction of quadriceps
    • Eccentric contraction of the quadriceps on a flexed knee
    • Examples: jumping sports, soccer, fall from elevation onto feet, bicycle accident


Risk Factors

  • Sports
    • Jumping
    • Running
    • Skateboarding

Differential Diagnosis

Clinical Features

  • History
    • Patients will have an acute injury
    • Typically a sudden, forceful contraction of the quadriceps muscle
    • No direct contact or blow to knee
    • They will endorse tenderness at the bottom of the knee cap
    • Pain or difficulty with knee extension
    • Inability to bear weight
  • Physical Exam: Physical Exam Knee
    • Antalgic Gait
    • Soft tissue swelling
    • Hemarthrosis/ joint effusion
    • On palpation, they will be tender at the the inferior pole of the patalla
    • High riding patella may be present
    • A gap or defect may be palpable
    • Patella may be high-riding
  • Special Tests


Lateral knee XR demonstrating patella alta and a 1.3cm ossific fragment representing an avulsion with partial rupture of the patellar sleeve.[6]


Knee US of the suprapatellar region shows a crescent-shaped echogenic fragment at the upper pole of the patella consistent with proximal pole avulsion fracture.[7]


  • Findings[8]
    • Disruption of cartilage
    • Measure degree of seperation
  • Secondary findings
    • Soft tissue edema and swelling
    • Joint effusion
    • Hyperemia


  • Indicated to best evaluate the degree of chondral injury


  • Based on direction of force acting on patella
    • Common: Inferior Pole Avulsion
    • Rare: Superior, Medial or Lateral Pole Avulsion



  • Goal
    • Achieve functional extensor mechanism
  • Indications
    • Nondisplaced or minimally displaced (< 2 mm) fractures
  • Recommend surgical consultation with pediatric specialist
  • Cylinder Cast with knee in extension
    • For 6 weeks


  • Indications
    • >2 mm displacement of the chondral- or osteochondral fragment
    • >2 mm articular step-off
    • Loss of extensor mechanism
  • Technique
    • Open reduction, internal fixation

Rehab and Return to Play


  • Needs to be updated

Return to Play

  • Needs to be updated

Complications and Prognosis


  • Risk of complications increases with greater degree of
    • Comminution
    • Displacement


See Also


  1. Gupta, Rishi R., et al. "Patellar sleeve fractures in children: a case report and review of the literature." American journal of orthopedics (Belle Mead, NJ) 35.7 (2006): 336-338.
  2. Bates DG, Hresko MT, Jaramillo D. Patellar sleeve fracture: demonstration with MR imaging. Radiology. 1994;193:825–7.
  3. Gao GX1, Mahadev A, Lee EH. Sleeve fracture of the patella in children. J Orthop Surg (Hong Kong). 2008 Apr;16(1):43-6
  4. https://radiopaedia.org/cases/69752
  5. Hunt, David M., and Naresh Somashekar. "A review of sleeve fractures of the patella in children." The knee 12.1 (2005): 3-7.
  6. Sullivan, Scott, Kevin Maskell, and Tristan Knutson. "Patellar sleeve fracture." Western Journal of Emergency Medicine: Integrating Emergency Care with Population Health 15.7 (2014).
  7. Hemeleers, Wouter, and Wim Siemons. "Superior sleeve avulsion of the patella." Journal of the Belgian Society of Radiology 102.1 (2018).
  8. Kimball MJ, Kumar NS1, Jakoi AM, Tom JA. Subacute superior patellar pole sleeve fracture. Am J Orthop (Belle Mead NJ). 2014 Jan;43(1):29-32.
Created by:
John Kiel on 7 July 2019 05:24:20
Last edited:
4 October 2022 15:57:13
Knee | Lower Extremity | Trauma | Pediatrics | Acute