Aortic knob

Dr Henry Knipe et al.

The aortic knob or knuckle refers to the frontal chest x-ray appearance of the distal aortic arch as it curves posterolaterally to continue as the descending thoracic aorta. It appears as a laterally-projecting bulge, as the medial aspect of the aorta cannot be seen separate from the mediastinum. It forms the superior border of the left cardiomediastinal contour.

Related pathology

The aortic knob may become enlarged in:

The aortic knob may be small or absent in:

The aortic knob may be obscured by:


Article information

rID: 61286
System: Vascular, Chest
Tag: refs, cases
Synonyms or Alternate Spellings:
  • Aortic knuckle

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Cases and figures

  • Figure 1
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  • Case 1: thoracic aortic aneurysm
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