A migrant was spotted with a knife in his waistband at the club I was working at. We attempted to get behind him to grab him before he pulled it, he saw the co worker circling behind as I introduced myself to him and brandished the blade. I this is Sparta teeped the shit out of him into a wall and my buddies jumped on him and pinned the knife hand. He was the only one to get hurt that night.
I'd never want to do one on one with a competent armed advisory though.
I have trained in knife fighting and defence. My favourite method for an equal fight was to wrap the left arm in one's coat, stand regular stance and use the knife as a straight right, parrying with the left.
One thing to consider is that you likely won't really feel small wounds with a knife in a fight. Many believe they were punched if they don't see it. As such going for the knife arm and suffering some damage on the way is an option, if one is pretty sure you out match them strength/skill wise.