The main problem in knife defence training is realising that the way you are likely to be attacked is entirely different from what most martial artists show. An entertaining video on YouTube of Jim Carey doing a Karate instructor sketch illustrates this point.  

Another problem is the fact that there are no guarantees in knife defence, and history shows that you are probably going to be cut in any attempted knife defence. All you can do is limit the areas of getting cut so you end up with a few stitches on your arms rather than severed arteries.

Back in the mid-1990s, when I put my Kyushindo Karate training on hold and tried Ju-Jitsu, the instructor in Gosport told me of an incident in a pub when he helped police calm down someone with a knife who was threatening everyone. In the brief struggle to restrain the knife wielder, using his skills, he got cut but did not notice the injury until afterwards. Until then, he thought his skills would help him escape unscathed, but this incident taught him that there are no guarantees.

Since then, I have always done a minimal amount of knife defence instruction. I remember the discussions with the other instructors when we made the Romsey Kyushindo Karate DVD back in 2002 regarding how much knife defence we should show. I was in favour of none, but I gave in to doing a few. I believe that it is not possible to defend against a knife-wielding attacker using unarmed techniques, and showing techniques that will never work would give a false sense of security to the student and the possibility of a terrible conscience if it ended in a fatality.

Unfortunately, some people don’t want to hear that there are no guaranteed techniques against knife attacks and that they are probably going to be cut.

Anyway, my research shows that the following is reasonable advice and observation:

1) If a weapon is suspected, you need to move closer before they can use it (see 3). A person carrying a knife typically intends to use it at close quarters.
2) If attacked suddenly in a straight line, the instinct to side-step does not exist under pressure.
3) Do not believe that you will have time to draw a weapon of your own. If you believe that someone is going for a knife, the only direction is forward and into them – they must be out of it before they know they are in it.
4) Once the knife is out, it is your priority to escape; otherwise, attack is the only defence.
5) It is accepted that once the knife is out:
a) You are likely to get cut and so should present the least important part of your body, such as the backs of your arms, raised as a guard.
b) The best you can hope for is to deflect the blade, enabling you to close and take him out of the game (elbows, eye gouges, throat strikes etc.)
c) If you can grab some clothing – good. Do not attempt a wristlock, as this is a ‘fine motor skill’ and is likely to fail.
d) Force the knife away from both bodies if you have managed to grab a sleeve—if you don’t, they will be able to manipulate the blade from the wrist and cut you, or worse, change the weapon to the other hand.
e) Your very first strike must have the maximum force and then strike again.
f) If an assailant simply pushes the blade close to you, you will usually be able to slap it out of their hand – action beats reaction.
g) Any knife held close and touching you must be attacked.
h) Compliance is no guarantee of not being cut.
i) A fast, non-telegraphed strike to the knife hand or arm will work – action beats reaction.