clasp-knife rigidity

rigidity

 [rĭ-jid´ĭ-te]

inflexibility or stiffness.

clasp-knife rigidity increased tension in the extensor of a joint when it is passively flexed, giving way suddenly on exertion of further pressure; seen especially in upper motor neuron disease. Called also clasp-knife reflex.

cogwheel rigidity tension in a muscle that gives way in little jerks when the muscle is passively stretched; seen in parkinson's disease.

decerebrate rigidity see decerebrate rigidity.

decorticate rigidity see decorticate rigidity.

paratonic rigidity an intermittent abnormal increase in resistance to passive movement in a comatose patient.

clasp-knife spas·tic·i·ty

a type of increased muscle tone due to a pyramidal tract lesion, in which abnormally increased resistance to passive stretch of a muscle abruptly decreases; typically, this appears near the end of the range of joint excursion.
See also: lengthening reaction.

Synonym(s): clasp-knife effect, clasp-knife rigidity

clasp-knife spas·ti·ci·ty

, clasp-knife rigidity (klaspnīf' spas-tis'i-tē, ri-jid'i-tē)

Initial increased resistance to stretch of the extensor muscles of a joint that give way rather suddenly, allowing the joint then to be easily flexed; the rigidity is due to an exaggeration of the stretch reflex.

clasp-knife spas·ti·ci·ty

, clasp-knife rigidity (klaspnīf' spas-tis'i-tē, ri-jid'i-tē)

Initial increased resistance to stretch of the extensor muscles of a joint that give way rather suddenly, allowing the joint then to be easily flexed; the rigidity is due to an exaggeration of the stretch reflex.