Fig. 14From: Chest imaging using signs, symbols, and naturalistic images: a practical guide for radiologists and non-radiologistsKnuckle sign. The figure clearly shows evident blood clot (black arrows) due to pulmonary embolism causing abrupt interruption of pulmonary arteries—in a patient affected by deep vein thrombosis. The abrupt interruption evokes the appearance of a knuckleBack to article page