Some time back I had the displeasure of attending a couple of SKD (spontaneous knife defense) classes.
I learned a couple of things.
1: You will get cut. Choose what you are willing to sacrifice/get cut, to assist you in your defense/attack.
2: Fighting with even a dummy knife hurts, a lot.
3: Person pulls a knife on me, they are going to be sporting a bunch of new holes in their hide. Many new holes.
Maybe from bullets, maybe from my knife.