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a sudden reflex or involuntary movement.
Achilles jerk (ankle jerk) plantar extension of the foot elicited by a tap on the achilles tendon, while the patient is seated on a bed or chair, with feet hanging freely; called also Achilles reflex and triceps surae jerk or reflex.
biceps jerk biceps reflex.
elbow jerk involuntary flexion of the elbow on striking the tendon of the biceps or triceps muscle.
jaw jerk jaw-jerk reflex.
knee jerk see knee jerk.
tendon jerk tendon reflex.
triceps surae jerk ankle jerk.
a sudden contraction of the triceps muscle caused by a smart tap on its tendon when the forearm hangs loosely at a right angle with the arm.