Spasticity is a condition in which there is increased
tension/tone in skeletal muscles, causing them to feel
and appear tight (resistant to stretch, excessive
contractions). Spasticity is usually associated with
decreased reflexes when the skin is stimulated but
increased reflexes when deep body structures, such as
tendons, are stimulated. Tendons are groups of muscle
fibers that attach muscles to a bone. Spasticity usually
involves the tendon extensors of the legs and the
flexors of the arms. Extensors are tendons that move
body parts outwards, whereas flexors are tendons that
move body parts inwards.
Spasticity of the hand.
FEATURED BOOK: Spasticity: Diagnosis and Management

In slight spasticity, gross movements may be coordinated smoothly, but combined
movements are impossible or appear uncoordinated. In moderate spasticity, movements
require great effort and a lack of coordination is present. Many people with spasticity
experience muscle weakness.

Common conditions that cause spasticity include multiple sclerosis, spastic diplegia, and
traumatic brain injury. Multiple sclerosis is a condition in which people develop multiple
areas of abnormal patches in the brain and/or spinal cord. Spastic diplegia is a
neuromuscular condition causing spasticity and increased muscle tone in the lower
extremities. Spasticity is a sign of upper motor neuron damage (e.g., upper motor neuron
"Where Medical Information is Easy to Understand"™
Upper motor neurons are neurons (nerve cells) in the motor cortex (an area of the brain located in middle,
top part of the brain) that form pathways within the brain and from the brain to the spine. The word
"spasticity" comes from the Greek word "spastikos" which means "drawing in." The "drawing in" part refers
to muscle movements that shorten or are drawn in during spasticity.