It is commonly known that frequently the patellar reflex cannot be obtained unless some special maneuver is employed to elicit it. The most usual means of reenforcing the knee jerk is the Jendrassik technic.1 By this method the patient is instructed to flex partially the fingers of each hand, to place the palmar surface of the flexed fingers of one hand against the palmar surface of the flexed fingers of the other hand and at the command of the physician to pull hard with the fingers of one hand on those of the other. As the patient thus pulls, the examiner taps the patellar tendon. By this procedure the amplitude of the reflex is usually increased, or a reflex which could not be secured by tapping the tendon alone is obtained. The reason for the success of the reenforcement maneuver is that as a result of it the attention
Marcus IH. COUGHING: A METHOD OF REENFORCING THE KNEE JERK REFLEX. Arch NeurPsych. 1935;34(6):1295–1296. doi:10.1001/archneurpsyc.1935.02250240164013
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