Hoover’s Sign is a clinical maneuver used in neurological examinations to determine the nature of a patient’s leg weakness or paralysis. First described in 1908 by Dr. Charles Franklin Hoover, this bedside test distinguishes between weakness caused by a physical, structural issue and weakness that is non-organic, often termed functional or psychogenic. The test provides evidence regarding the integrity of the underlying motor pathways by leveraging a normal physiological phenomenon. It is a quick, non-invasive assessment.
The Principle Behind Hoover’s Sign
The foundation of Hoover’s Sign lies in the natural motor control concept known as involuntary synergy. When a healthy person consciously attempts to lift one leg, the opposite leg’s extensor muscles contract automatically and unconsciously. This involuntary action causes the opposite heel to press downward against the supporting surface, stabilizing the body during the effort. This compensatory, downward extension force is a normal reflex mechanism mediated through intact motor pathways, including the corticospinal tract. The presence of this automatic, unconscious effort confirms that the motor command pathways are functionally intact.
How the Hoover’s Sign Test is Performed
The test begins with the patient lying flat on their back (supine). The clinician positions themselves at the patient’s feet and places one hand underneath the heel of each leg to detect downward pressure.
The test is performed in two steps, first focusing on the allegedly weak leg. The patient is instructed to lift the weak leg off the table while the clinician monitors the pressure exerted by the heel of the strong leg. Next, the patient is asked to lift the strong leg against resistance, and the clinician feels for involuntary downward pressure from the heel of the weak leg.
What a Positive Result Indicates
A “positive” Hoover’s Sign is identified by a specific pattern suggesting a non-organic cause for the weakness. This occurs when the patient cannot lift the weak leg, and the clinician does not feel the expected involuntary downward pressure from the strong leg’s heel. This suggests the patient is not exerting a maximal effort, as the synergistic reflex is not triggered.
The test is confirmed as positive when the patient is then asked to lift the strong leg, and the clinician does feel involuntary downward pressure from the heel of the weak leg. This functional inconsistency shows that the motor pathways for the weak leg are working when triggered unconsciously. A positive sign is highly specific for functional neurological disorder, indicating the paralysis is not caused by a structural lesion.
The Significance of a Negative Hoover Sign
The determination of a “negative” Hoover’s Sign is made when the expected involuntary synergistic contraction is not present in the weak leg during the test. Specifically, when the patient attempts to lift their strong leg, the clinician does not feel the heel of the weak leg press downward. This means the normal, automatic extensor response is absent or significantly reduced.
The absence of this involuntary pressure strongly suggests that the weakness is “organic,” meaning it is likely caused by actual physical disruption or damage to the nervous system. This type of weakness is consistent with conditions that impair the motor control pathways, such as a stroke, multiple sclerosis, or a compressive spinal cord lesion. In these cases, the neurological injury prevents the motor signal from reaching the muscles, regardless of whether the effort is conscious or unconscious.
A negative result is a starting point for a more focused medical investigation to identify the underlying structural pathology. While the test is highly specific, it is not a definitive diagnostic tool on its own. Further diagnostic testing, which may include magnetic resonance imaging (MRI) or electromyography, is required to confirm the precise nature and location of the organic disease. A negative Hoover’s Sign directs the diagnostic process toward identifying a verifiable neurological or structural cause for the patient’s weakness.