The knee was beautiful and accurate, but remember just because a shot drops you or hurts you it doesn't automatically mean the fight is over, far from it, you gotta let it play out.
Thats why I have always been a big fan of Jason Herzog, he understands that this is supposed to be Ultimate Fighting and thats what you're supposed to do, hurt people!. He gets it and doesn't freak out when someone gets rocked. A lot of the refs freak out way too easily, Herzog is one of the better ones for sure, doesn't freak out so easily.