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Patellar fracture
Other Resources UpToDate PubMed

Patellar fracture

Contributors: Robert Lachky MD, Eric Ingerowski MD, FAAP
Other Resources UpToDate PubMed


The patella is the largest sesamoid bone in the body, and it functions to direct the forces exerted by the quadriceps muscles. Patients with patella fracture will have pain / swelling over the knee with large knee effusion and tenderness over the patella.

Fracture can be caused by direct or indirect forces.
  • Direct impact to patella can occur from a fall on a flexed knee landing directly on patella or motor vehicle crash. This can result in a transverse fracture pattern (more common in younger adults) or a comminuted fracture (more common in elderly patients and those with osteoporotic bone).
  • Indirect impact can occur with sudden flexion of the knee against a contracted quadriceps muscle (depending on the force and properties of the muscle / bone / tendon, something in the patient's extensor mechanism will break, whether it is the quadriceps tendon, the patellar tendon, or the patella itself). Avulsion fractures involve the superior / inferior pole.
Osteochondral lesion of patella is discussed separately.


S82.009A – Unspecified fracture of unspecified patella, initial encounter for closed fracture

51037009 – Fracture of patella

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Bipartite patella (these are normal anatomic variants; 20% of the time, the patella will develop from 2 or 3 ossification centers instead of 1)
  • Patellar dislocation (medial patellofemoral ligament disruption)
  • Patellar subluxation
  • Quadriceps tendon rupture
  • Patellar tendon rupture
  • Quadriceps tendinopathy
  • Patellar tendinopathy
  • Tibial plateau fracture
  • Long bone fracture

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Last Reviewed:06/27/2019
Last Updated:03/25/2021
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Patellar fracture
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