- clasp-knife rigidity
- an exaggerated stretch reflex of skeletal muscles seen in spasticity and decerebrate rigidity, resembling the opening of a penknife or clasp knife; there is increased resistance to the extensors (induced by passive flexion of a joint), which suddenly gives way on exertion of further pressure. Called also clasp-knife effect, phenomenon, reflex, or spasticity.
Medical dictionary. 2011.