Reminds me, forget the Sharpie and write on a post it note 'THIS One!', stick it on you knee before they come to wheel you in. If anyone in the OR has a sense of humor you'll hear 'wow, good catch mate! We were going to operate on the other knee.'
Good luck.
"Take a bus! Don't walk!!" But i'm in training for a new knee, eh. It will be about a 2.8 mile hobble. Fitness counts.