Doesn't for me. At LHR, the British agent looked at my "picture" and said he had to check my leg (metal inplant with long screws). He did so, and then said, "Oh, it is quite swollen". I concurred. I seem to get the pat down every time using the mm wave, but only about 1/2 the time with the WTMD. Often, I don't set off an alarm (maybe due to the titanium not being a ferrous metal??).