aortic knob
The visible prominence of the aortic arch on chest X-ray, used to assess for aortic pathology including dissection, aneurysm, or mediastinal widening.
Full Definition
The aortic knob, also called aortic knuckle, represents the left lateral border of the aortic arch as seen on frontal chest radiographs. In emergency cardiology, changes in the aortic knob's appearance—including widening, irregularity, or loss of definition—may indicate acute aortic pathology such as dissection, traumatic injury, or aneurysm expansion. A widened or abnormal aortic knob, particularly with mediastinal widening greater than 8cm, raises suspicion for aortic emergency requiring immediate advanced imaging and cardiovascular surgery consultation.
Usage
Usage note: Often used interchangeably with 'aortic knuckle' in radiology reports.
In Context
- "The chest X-ray showed widening of the aortic knob concerning for possible aortic dissection." — Emergency radiology report
- "Evaluate the aortic knob contour for signs of acute aortic pathology." — Imaging interpretation protocol