Patellar fracture

Last revised by Karen Machang'a on 6 Jan 2024

Patellar fracture is one of the common knee injuries usually post direct trauma to the patella or sudden forceful contraction of the quadriceps muscles in the context of a sports injury.

Fractures of the patella represent ~1% of all fractures and are most common in those aged 20-50 years. Two-thirds of cases are in males 7.

Patients present with marked swelling and pain over the patella with point tenderness and marked reduction in extension strength. Usually, there is a large joint effusion or hemarthrosis.

  • stiffness
  • weak extensor mechanism
  • degenerative disease of the patellofemoral joint

There are different causes of patella fracture:

In practice, often both direct and indirect mechanisms are important, e.g. a direct trauma coupled with a forceful contraction of the quadriceps 7.

Some fractures are more subtle and need to be differentiated from normal variants.

Treatment is determined by the amount of displacement of the fracture and whether the extensor mechanism of the knee is intact or disrupted.

For patients with a nondisplaced or minimally displaced fracture and an intact extensor mechanism, nonoperative treatment may be suitable. This usually involved a Zimmer knee splint for 4-6 weeks. The patient is usually allowed to weight bear in the splint during this period 6.

In the case of displaced fractures or disrupted extensor mechanism, surgical management is usually required 6. The surgical treatment of these fractures usually involves tension band wiring (K wire technique).

The main differential is of multipartite patella, where there is a failure of fusion of secondary ossification centers. The unfused fragments are almost always in the superolateral quadrant of the patella. With a multipartite patella, the volume of the true patella plus that of the smaller ossification centers is greater than that expected of a normal patella. With a patellar fracture, the volume of the fractured components is equivalent to that of a normal patella.

Rarely a traumatic separation of a multipartite patella may occur 7.

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Cases and figures

  • Case 1: transverse fracture
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  • Case 2: transverse fracture
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  • Case 3: transverse fracture
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  • Case 4: inferior pole comminuted fracture
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  • Case 5: comminuted fracture
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  • Case 6: comminuted fracture
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  • Case 7: vertical fracture
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  • Case 9: vertical fracture
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  • Case 10: vertical fracture
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  • Case 8: vertical fracture
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  • Case 12: non-displaced patellar fracture (MRI)
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  • Case 11: non-displaced fracture (MRI)
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  • Case 13: fracture and dislocation
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  • Case 14: tension band wiring
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  • Case 15
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