How to defend against a knife attack
A "knife fighter" is a person who uses a knife to fight. He or she relies solely on the knife as a weapon of intimidation, usually because he or she is not intimidating without the weapon. Without the knife, the knife fighter would lose his or her power over victims. However, a person who is a trained fighter who fights well, will use a knife in a fight if it is available, but does not need a knife or any other weapon to feel confident and in control during a fight. Since most bad guys are not trained to fight, with or without a knife, if you are confronted by a person with a knife, he or she is most likely a knife fighter. When facing a knife wielder, the threat is not so much from the knife itself as from the brain of the person holding the knife. An idiot with a knife is less a threat than a person who is trained to fight and has a knife.
A knife has a short range, the attacker's reach plus the length of the blade, So, when facing a knife, whenever it is possible, simply run away! If you cannot run, then your must immediately attack the attacker.
Your primary weapon is your brain. If you are thinking better and faster than your attacker, you have an advantage. Your next weapon is your body: your arms, legs, hands, feet, elbows, knees, and skull. Lastly, available objects may be used as weapons, whether or not that is their intended purpose. Since the brain is needed for the body to be used as a weapon and it is needed to use an object as a weapon, the first target of a counterattack should be the attacker's brain, or central nervous system.