Dorsal defect of the patella

Last revised by Dr Mostafa El-Feky on 22 Jun 2022

Dorsal defects of the patella are benign subchondral lesions of unknown etiology and a normal developmental anomaly of the patella, which can be mistaken for a pathological process such as a focus of infection or osteochondritis dissecans.

Dorsal defect of patella occurs in males and females with equal frequency and is most frequently found in adolescents. It is bilateral in up to one-third of individuals.

This condition often is asymptomatic and an incidental finding on knee imaging, but it occasionally may be the cause of knee pain.

A rounded focus of radiolucency surrounded by a sclerotic margin in the superolateral quadrant of the patella.

On MR, this defect is similar to many other bony lesions:

  • T1: low signal 
  • T2: high signal

Notably, the lesion has a sclerotic rim and is usually not associated with marrow edema, although this has been very rarely reported 7. The overlying cartilage is usually but not always intact 7.

A dorsal defect of the patella is one of the skeletal "do not touch" lesions, therefore because of its characteristic location, it should not undergo biopsy. 

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Cases and figures

  • Case 1
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  • Case 2
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  • Case 3
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  • Case 4
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  • Case 5
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  • Case 6: with bone marrow edema
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  • Case 7
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