Why Do Doctors Really Hit Your Knee with a Tiny Rubber Hammer?

Sure, sure, to test your reflexes. Everybody knows that. Isn’t the delayed kick in the pants when the doctor turns his back a slapstick mainstay? Harpo invented it. Or was it Curly?

Anyway, testing reflexes is the objective, but why hit that little sweet-spot below the kneecap specifically? Why doesn’t Dr. Feelgood just lob a quick sucker-punch at you to check your flinch factor?

For starters, the knee gets top billing in the reflex test for one simple reason: it’s easy to access. You’re sitting on the table in that backless gown, fighting humiliation and cold. It’s merciful that nobody’s asking you to hop on one leg while you pat your head and rub your belly. There’s your knee in all its unadorned glory. Sit tight, this won’t hurt a bit.