A No Nonsense Way to Defeat a Criminal
What happens if we have an attacker who has a knife and we are unarmed? What I am not going to teach you is some multi-step joint lock where you catch the attacker's hand in midair and lock up their fingers into a pretty "Hollywood move. Those are "fine and complex" muscular movements that don't work when you have adrenaline rushing through your system. Let me repeat, they are physically impossible to do as your rush of adrenaline will shut down the ability to perform those detailed movements.
What you need is "gross" motor skill movements that are general movements that focus on large muscle groups. So, I'm going to show you a simple three step process that when practiced against different attacks will give you a direct line to securing the attacker's knife, taking them out of commission and giving you full control.
The three-step strategy to remember when dealing with this situation is Distance, Isolate, and Terminate. Distance means that when the attacker swings, slashes or stabs at you, you need to be far enough away to evade the knife, but close enough so that when the blade passes you can close the gap. Once the knife passes you and starts to return to the attacker, then is the time to close the gap and isolate.
We close the gap because when facing a weapon of any sort being at a distance is where you are at a disadvantage. Being close to the opponent and "jamming" their ability to move is where your greatest defense and counter attack lies. So, once again, when the attacker strikes past you, then we rush in to our next step, which is to isolate the weapon arm. This is where we grab the attacker's weapon arm with both of our hands, securing control over it.
The third and final steps is to terminate. We end the altercation not by simply seizing the arm, but by using this closer range to use our ballistic tools, such as knees, elbows and head butts. Striking our opponent using these moves will provide the best bang for your buck, increasing your leverage and damage on the opponent. My only caveat is to make sure you leave the elbow strikes until last, as you will have to release your hold in order to elbow strike.
In other words, you've spent the time and energy getting into that close range, dodging the knife attack and securing the weapon arm, the last thing you want to do is to have to let go of that dangerous limb in order to strike your attacker. I'm not saying to pass up on the elbow strike as it is a powerful tool, but simply use it at the end of your strikes, softening up our opponent first with knee strikes and head butts.
Distance, Isolate and Terminate is not just about "techniques", but having the attributes to pull it off in real life. The point being, you have to put in some practice time in order to develop the timing and proper angles to protect yourself while inflicting as much damage as possible. The help you better understand these techniques I have put together a short video series that walks you through these moves.