Definition of Hoover sign

Hoover sign

1. when a subject lying supine is asked to raise one leg, he or she involuntarily creates counterpressure with the heel of the other leg; if this leg is paralyzed, whatever muscular power is preserved in it will be exerted in this way; or if the patient attempts to lift a paralyzed leg, counterpressure will be made with the other heel, whether any movement occurs in the paralyzed limb or not; not present in hysteria or malingering;
2. a modification in the movement of the costal margins during respiration, caused by a flattening of the diaphragm; suggestive of empyema or other intrathoracic condition causing a change in the contour of the diaphragm.