Eliciting knee jerk--a new method of reinforcement.

This study was designed to detect the sensitivity of different methods of eliciting knee jerks and to compare the conventional methods with the newly purposed maneuver. Knee jerk (a deep tendon reflex) was elicited in 123 apparently normal population (77 males and 46 females) with three different methods (1) without applying reinforcement, (2) applying Jendrassik maneuver (strong voluntary contraction of upper limbs) and (3) using the new method of reinforcement--that is by dorsiflexion of ankle joint of the same foot voluntarily as strong as possible on which the jerk would be elicitated. The sensitivity of the method without reinforcement was found to be is 87.8%; that with Jendrassik maneuver was 93.5%, whereas the sensitivity of newly proposed maneuver was 99.2%. Results of the present study have served to demonstrate that elicitation of knee jerk with newly proposed reinforcement maneuver is the best among all three methods.