As you know, I had a knee replaced a few months before last year's Sindo. Every time, I travel in the United States, I get secondary automatically.
Normally I tell the screener that it is a knee replacement and just walk past to enter the corral. Not my last time at LAX where it came close to arrest because I did what I normally do and the "description of screener deleted" accused me of shoving her. It took management intervention to get me to the AS Boardroom on time.

BTW: the problem is only in the U.S. (and possibly Canada-my travels have not taken me there since the knee) and not anywhere else including tough places like SIN, BKK and NRT. In fact, often outside the U.S. the alarm does not even sound.

What I find really offensive is that they not only wand, but do a double pat down. That is besides ignoring those of us who may be in the corral waiting for screening. Showing your scar is not effective, they still are just as obnoxious. BTW: According to the latest posted TSA guidelines for passengers, the pat down is unnecessary, but always done.

Best of luck to your other half, she will be much more mobile even though the pain may not totally go away.