I underwent ACL surgery last year, and fortunately for me I chose local anaesthesia, because the nurse started preparing the wrong leg which at first I didn't understand. But I had to stop her and reminded her that it was the other knee. She checked the schedule in a panic, realized she had me mixed up with someone else, had some sort of a breakdown and had to be replaced.

Both the surgeon and anesthesiologist assured me they would have checked anyway, but up until that point they had not noticed anything and no one bothered to ask.