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1. alternate involuntary muscular contraction and relaxation in rapid succession.
2. a continuous rhythmic reflex tremor initiated by the spinal cord below an area of spinal cord injury, set in motion by reflex testing.
ankle clonus (foot clonus) a series of abnormal reflex movements of the foot, induced by sudden dorsiflexion, causing alternate contraction and relaxation of the triceps surae muscle.
toe clonus abnormal rhythmic contraction of the great toe, induced by sudden passive extension of its first phalanx.
wrist clonus spasmodic contraction of the hand muscles, induced by forcibly extending the hand at the wrist.
alternating movements of flexion and extension of the great toe after forcible extension at the metatarsophalangeal joint.
Etymology: AS, tá + Gk, klonos
an increased reflex activity in the large toe caused by a sudden extension of the first phalanx.
Contraction of the big toe caused by sudden extension of the first phalanx.
See also: clonus