Pronator quadratus sign

Dr Henry Knipe et al.

The pronator quadratus sign can be an indirect sign of distal forearm trauma. It relies on displacement of the fat pad that lies superficial to the pronator quadratus muscle.

Displacement, anterior bowing, or obliteration of the fat plane in the setting of trauma may indicate a distal radius or ulna fracture. Various studies have described a high specificity but wide-ranging sensitivity for fracture ranging from 26 to 98%; thus a negative pronator quadratus sign does not exclude fracture 1,2,4.

In the absence of trauma, there are other causes for a positive pronator quadratus sign:

On lateral wrist radiographs, the pronator fat pad normally appears as a thin radiolucent triangle, with its base attached to the palmar surface of the distal radius 1,2. It is observed ~90% of the time 1. One study 4, has suggested a cut-off of <8 mm (female) and 9 mm (male) on lateral x-rays as a cut-off for normal.

It was first described by MacEwan in 1964 3.

Article information

rID: 26112
Section: Signs
Synonyms or Alternate Spellings:
  • Pronator quadratus fat pad sign
  • Obliteration of pronator quadratus fat plane

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Cases and figures

  • Case 1: normal
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  • Case 1: annotated
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  • Case 2: anterior bowing
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  • Case 3: displacement
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  • Case 4
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  • Case 5
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