Patellar Fractures

Epidemiology

  • About 1% of all fractures
  • Direct blow or eccentric quadriceps contraction against a flexed knee

Classification

Descriptive

TypeDescription
TransverseMost common, often from indirect quadriceps loading
Upper or lower poleExtra-articular avulsions of quadriceps or patellar tendon
Vertical or marginalDirect load in flexion, extensor mechanism usually intact
Stellate or comminutedDirect blow, often with cartilage damage
OsteochondralAfter patellar dislocation, medial facet or lateral femoral condyle
Sleeve fractureIn children, cartilage avulsed from the lower pole with a small bony fragment
  • Displacement means an articular step over 2 mm or a gap over 3 mm

AO/OTA 34

TypeDescription
34AExtra-articular, including pole avulsions and body fractures sparing the articular surface
34BPartial articular vertical fractures of the medial or lateral facet
34CComplete articular, from simple transverse (C1) through extra fragment (C2) to comminuted (C3)

Original publication Meinberg EG, Agel J, Roberts CS, Karam MD, Kellam JF. Fracture and Dislocation Classification Compendium-2018. J Orthop Trauma. 2018;32 Suppl 1:S1-S170.

Investigations

Patellar Fractures, tension band wiring of a transverse patella fracture
Tension band wiring of a transverse patella fracture. Image by Hellerhoff, Wikimedia Commons, CC BY-SA 3.0.
  • AP, lateral and skyline views
  • Skyline detects vertical and marginal fractures missed on AP and lateral
  • CT defines comminution and articular involvement before fixation
  • Bipartite patella is superolateral, bilateral, with smooth sclerotic margins, and should not be called a fracture

Management

  • Straight leg raise against gravity tests extensor mechanism integrity
  • Undisplaced with intact mechanism, hinged brace or cylinder cast in extension with early weight bearing
  • Displaced transverse, tension band wiring, often over cannulated screws
  • Displaced vertical, interfragmentary lag screws
  • Comminuted, plate fixation, cerclage or both
  • Unfixable comminuted pole, partial patellectomy with tendon reattached near the articular surface
  • Osteochondral fragments fixed if large, excised if small, with stabilisation where indicated
  • Total patellectomy reserved for unreconstructable injuries

Complications

  • Symptomatic hardware is the commonest reason for further surgery
  • Post-traumatic patellofemoral arthritis is common after articular injury

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.