This is going to be me in a couple of weeks. We are flying on Sept. 1st. I have had both of my knees replaced and set off the alarm when I flew a couple of years ago. I tried to show the cards I got from my doctor, but they weren't interested. I was wanded and patted down. I'm sure I will be strip-searched this time. I'll let you know what happens. Oh, BTW -- I'm a 5'0", 50 something white woman.
The people who go through packed luggage in the name of security (and the reason we cannot lock checked bags) also have been caught stealing from that same luggage.
It is more procedural than genuine security.