Jendrassik maneuver is a reflex seen when the patient is asked to clench his teeth and flex his arm and interlock his fingers. The patellar tendon is then striked and it elicits patellar reflex. This reflex is then compared to normal patellar reflex. The maneuver is done to distract patient attention and increase the reliability of the results. It increases the myotatic reflex. Exaggerated patellar jerk can be seen in upper motor neuron lesions, hyperthyroidism or anxiety.