cogwheel rigidity

noun

cog·​wheel rigidity ˈkäg-ˌ(h)wēl- 

: muscular rigidity in which passive movement of the limbs (as during a physical examination) elicits ratchet-like start-and stop movements through the range of motion of a joint (as of the elbow) and that occurs especially in individuals affected with Parkinson's disease

The third major sign, rigidity (sometimes called "cogwheel" rigidity), is peculiar to Parkinson's disease. When a limb is bent, it seems to catch at regular points throughout its range of motion, much as a second hand jerks from interval to interval instead of smoothly traversing the face of a clock.

—Harriet Washington, The Harvard Medical School Health Letter

called also cogwheeling