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Patellar Pole Avulsion Fracture
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Contents
Other Names
- Patellar Sleeve Fracture
- Patellar Sleeve Avulsion Fracture
- Patellar Sleeve Avulsion (PSA)
- Pediatric Patellar Avulsion Fracture
- Sleeve fracture of the patella
Background
- 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
History
Epidemiology
- 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]
Pathophysiology

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
Pathoanatomy
- Patella
- Extensor mechanism: Quadriceps attaches to Patella, Patella Tendon inserts on Tibial Tubercle
- Ossification begins at 3-5 years
- Patella sleeve fracture
- Involves separation of articular cartilage, retinaculum, periosteum, osseous fragment
Risk Factors
- Sports
- Jumping
- Running
- Skateboarding
Differential Diagnosis
- Fractures
- Dislocations & Subluxations
- Patellar Dislocation (and subluxation)
- Knee Dislocation
- Proximal Tibiofibular Joint Dislocation
- Muscle and Tendon Injuries
- Ligament Pathology
- Arthropathies
- Bursopathies
- Patellofemoral Pain Syndrome (PFPS)/ Anterior Knee Pain)
- Neuropathies
- Other
- Bakers Cyst (Popliteal Cyst)
- Patellar Contusion
- Pediatric Considerations
- Patellar Apophysitis (Sinding-Larsen-Johnansson Disease)
- Patellar Pole Avulsion Fracture
- Tibial Tubercle Avulsion Fracture
- Tibial Tuberosity Apophysitis (Osgood Schalatters Disease)
- Proximal Tibial Metaphyseal Fracture
- Proximal Tibial Physeal Injury
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
- Straight Leg Raise: Will have difficulty, may be unable to perform
Evaluation

Lateral knee XR demonstrating patella alta and a 1.3cm ossific fragment representing an avulsion with partial rupture of the patellar sleeve.[6]
Radiographs
- Standard Radiographs Knee
- Findings
- Swelling at the lower pole of the patella
- Patella Alta (Patella Baja in proximal fractures)
- Bony fragment may avulse off (can easily be missed)
- Fracture line through the patella
- +/- joint effusion

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]
Ultrasound
- Findings[8]
- Disruption of cartilage
- Measure degree of seperation
- Secondary findings
- Soft tissue edema and swelling
- Joint effusion
- Hyperemia
MRI
- Indicated to best evaluate the degree of chondral injury
Classification
- Based on direction of force acting on patella
- Common: Inferior Pole Avulsion
- Rare: Superior, Medial or Lateral Pole Avulsion
Management
Nonoperative
- 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
Operative
- 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
Rehabilitation
- Needs to be updated
Return to Play
- Needs to be updated
Complications and Prognosis
Prognosis
- Risk of complications increases with greater degree of
- Comminution
- Displacement
Complications
- Patella Alta
- Anterior Knee Pain
- Loss of quadriceps function
- Extensor Lag
- Malunion or nonunion
- Development of ectopic bone
- Avascular Necrosis
See Also
- Internal
- External
- Sports Medicine Review Knee Pain: https://www.sportsmedreview.com/by-joint/knee/
References
- ↑ 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.
- ↑ Bates DG, Hresko MT, Jaramillo D. Patellar sleeve fracture: demonstration with MR imaging. Radiology. 1994;193:825–7.
- ↑ Gao GX1, Mahadev A, Lee EH. Sleeve fracture of the patella in children. J Orthop Surg (Hong Kong). 2008 Apr;16(1):43-6
- ↑ https://radiopaedia.org/cases/69752
- ↑ Hunt, David M., and Naresh Somashekar. "A review of sleeve fractures of the patella in children." The knee 12.1 (2005): 3-7.
- ↑ Sullivan, Scott, Kevin Maskell, and Tristan Knutson. "Patellar sleeve fracture." Western Journal of Emergency Medicine: Integrating Emergency Care with Population Health 15.7 (2014).
- ↑ Hemeleers, Wouter, and Wim Siemons. "Superior sleeve avulsion of the patella." Journal of the Belgian Society of Radiology 102.1 (2018).
- ↑ 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
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Last edited:
4 October 2022 15:57:13
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