Knuckle sign (pulmonary embolism)

The knuckle sign refers to the abrupt tapering or cutoff of a pulmonary artery secondary to an embolus. It is better visualized on CT pulmonary angiography (CTPA) than chest x-ray. This is an important ancillary finding in pulmonary embolism (PE), and often associated with the Fleischner sign of dilated central pulmonary arteries. 

It is one of several described signs of pulmonary embolus on chest radiographs.

See also

Article information

rID: 41201
System: Chest
Section: Signs
Synonyms or Alternate Spellings:
  • Knuckle sign: pulmonary embolism
  • Knuckle sign in pulmonary embolism

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