I think the piece of metal that zings out of Hillary's pant leg just prior to her collapse is a big deal. It fell with a 'zing' and not a 'ping', as if it slid down a rod on its way to the ground. She immediately buckled and had to be thrown into ambulance-van.

I'd like someone with a little medical knowledge to chime in here: My best guess is some kind of pelvic brace that supports her hips, or keeps her knees locked.