ok, so the screeners "know ahead of time" that you have a knee brace and that it will alarm.

if you go thru the wtmd and you alarm, you should get secondary and i have no problem with that

what i have an issue with is how long it took and how it was done. it would have been much simpler if:

a) the tsa let you take the knee brace off, put it thru x-ray and go the wtmd a second time (and iirc, every one gets a second chance for things like loose change in the pocket and belt buckles)

b) you told the screener it would be much easier if you dropped trou and began to loosen your belt. two hockey pucks says that would get their attention quicker than they could yell "bravo"