The abductor sign is a useful test to detect non-organic paresis because it is difficult for a hysterical patient to deceive the examiner, the hip abductor is one of the most commonly involved muscles in pyramidal weakness, and the results are easily visible as movement or non-movement of the unabducted leg.
To test the abductor sign, the examiner told the patient to abduct each leg and opposed this movement with his hands placed on the lateral surfaces of the patient’s legs. The leg contralateral to the abducted one showed opposite actions for organic paresis and non-organic paresis: for example, when the paretic leg was abducted, the sound leg stayed fixed in organic paresis but moved in the hyperadducting direction in non-organic paresis. Hoover sign was used for comparison in the same patients.