knob sign

knob sign

A reduced or absent aortic “knob” on a plain AP chest film, a finding typical of secondary atelectasis of the left lower lobe of lung.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

knob sign

Imaging A ↓ or absent aortic 'knob' on a plain AP CXR, a finding typical of 2º atelectasis of the left lower lobe of lung
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.