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Spasticity vs. Rigidity
Characteristics & Causes of Spasticity
- Clasp-knife phenomenon: The limb experiencing spasticity suddenly gives way after an initial resistance to movement. Much like how a clasp-knife slightly resists before folding in. This can be caused by over-stretching the joint or muscles (during initial movement), the inverse stretch reflex (during sustained movements), and eventually contractures (a condition wherein muscles shorten/harden).
- Stroking effect: One may experience relief from episodes of spasticity by stroking the affected muscle’s surface, although this will likely not provide relief from contracture.
- Distribution: The sensation of spasticity is distributed differentially, often affecting antigravity muscles (muscles which are the extensors of the back, hips, and knees, which help to maintain proper posture by resisting the pull of gravity).
- Amyotrophic lateral sclerosis
- Brain damage resulting from insufficient oxygen
- Spinal cord injury
- Traumatic brain injury