As my (big, bodybuilding) client was turning over onto his back during the massage, he TOTALLY kneed me in the thigh. Ow. I was grimacing and silently screaming, hoping he'd keep his eyes closed so he wouldn't freak out and think I was having a seizure or something.
Then he apparently realized he'd made secondary contact because he muttered a "Sorry..."
Hey, at least he's a good tipper!