Clonus (from the Greek for violent, confused motion) is a series of involuntary, rhythmic, muscular contractions and relaxations.
Clonus, also called clonospasm, is the medical term for repetitive, involuntary muscular contractions due to sudden stretching. It most commonly affects the ankles. Clonus takes its name from a Greek word meaning tumult and is often a symptom of neurological disorder. Clonus commonly affects the ankles and involves repetitive, involuntary muscular contractions. Lesions caused by multiple sclerosis may lead to clonus. Monoamine oxidase inhibitors (MAOIs) and other antidepressants can contribute to serotonin syndrome, which is sometimes associated with clonus. Clonus: An involuntary muscular contraction and relaxation in rapid succession. See detailed information below for a list of 23 causes of Clonus, Symptom Checker, including diseases and drug side effect causes. » Review Causes of Clonus: Causes | Symptom Checker ».  Clonus is most commonly found at the ankle, specifically with a dorsiflexion/plantarflexion movement (up and down). Some case studies have also reported clonus in the finger, toe, and laterally in the ankle (as opposed to the typical up and down motion). 1  Ankle (medial gastrocnemius). 2  Patella (knee cap). Studies have shown clonus beat frequency to range from 3–8 Hz on average, and may last a few seconds to several minutes depending on the patient’s condition. 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. wrist clonus spasmodic movement of the hand, induced by forcibly extending the hand at the wrist. 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 An ankle clonus is a movement disorder characterized by involuntary waves of muscle contractions in the ankle, occurring in response to stretching the muscles in and around the ankle. It is usually a sign of a neurological disorder, as the body normally prevents such contractions from occurring.  Clonus is a sign of certain neurological conditions, particularly associated with upper motor neuron lesions involving descending motor pathways, and in many cases is, accompanied by spasticity (another form of hyperexcitability). Studies have shown clonus beat frequency to range from 3–8 Hz on average, and may last a few seconds to several minutes depending on the patient’s condition. clonus. 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. 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. 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. Clonus (from the Greek for violent, confused motion) is a series of involuntary, rhythmic, muscular contractions and relaxations. Studies have shown clonus beat frequency to range from 3–8 Hz on average, and may last a few seconds to several minutes depending on the patient’s condition. 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. 
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what is clonus