Golgi Renshaw

What do muscle spindles, golgi tendon organ, and renshaw cells have to do with spasticity?

In brief, muscle spindles record the change in length and trigger the stretch reflex.  Golgi tendon organs regulate muscle contraction to cause equal tension throughout the movement.  Renshaw cells control the stretch reflex by preventing overactivity of the stretch receptors.  In spasticity, muscle spindles are unable to send the appropriate message to the brain about the change in muscle length.  Golgi tendons are unable to regulate muscle contraction causing inability to relax or slowly contract.  Renshaw cells lose ability to inhibit excessive stretch reflex.  The pathophysiology of spasticity can be reviewed here.