What feature best distinguishes rigidity from spasticity?

• A. Rigidity shows constant resistance that is not velocity-dependent.
• B. Rigidity is velocity-dependent and spasticity is constant.
• C. Spasticity shows decreased reflexes.
• D. Both present with reduced ROM.

Answer: (A)

The defining feature is that rigidity produces a constant, non–velocity-dependent resistance to passive movement, while spasticity is velocity-dependent—the resistance increases as you move the limb faster. This means rigidity feels the same whether you move slowly or quickly, whereas spasticity ramps up with faster stretches due to hyperexcitable stretch reflexes (often with brisk reflexes and sometimes clonus). The other statements don’t fit: spasticity isn’t typically associated with decreased reflexes, and the idea that both have reduced ROM isn’t the key distinction.