I'm not going to go into great detail about my experience with knives, but I suppose this reassures some people that I know what I'm talking about. Growing up in Manchester, I witnessed a knife attack from a distance. When I had to face a blade myself, I was relatively lucky. My attacker was drunk, and seemingly unsure about whether they really wanted to cut me or put a hole in me. In that situation, the judo I had learned up to that point, combined with some necessary improvisation, was enough for me to gain control of the situation. I escaped unharmed. This is unusual.
I apologise for any offence I may cause here, but the eskrima class I attended was a disappointment. I can tell you that Filipino martial arts have excellent knife survival techniques but, like with everything else, this can be undone by poor teaching methods. Many of the "knife defence" techniques I have seen are useful, but I see them being poorly implemented. At worst, I see things which give a false sense of security, and may just get someone killed.
I will give credit to the instructors who say that the preferred option is always to run. The only exception to that rule is where escape is not possible. If an instructor neglects to mention this most important point, you should question whether they can reasonably be regarded as an expert on surviving a knife attack.
Rather than give you some set defences, which would be of limited use, I'm going to give you some principles. The same principles are useful for an attack by any weapon, bladed or otherwise, including empty hands and feet.
1. Don't be thereAs previously stated, escape is always the preferred option. The outcome of any encounter is always unknown, but a blade certainly stacks the odds in favour of the person holding the blade. If escape is not possible, or the knife-wielding fiend is already close enough to make the attack, mobility is the key. Your first priority must always, always be to get out of the weapon's way. Those footwork drills that everyone neglects, because they want to get to the "fun" stuff - think of them as your best friend. Whether you run, side step, move out of range or use a redirection technique, the principle is still the same: get out of the way.
2. DefenceIf you have managed to get out of the weapon's path, and especially if you haven't, controlling the path of the weapon is your next priority. The two ways of doing this are to stop the weapon or to redirect the weapon. Redirection is always the better option, because stopping the weapon's motion relies on the momentum of your block being greater than that of the weapon, whereas redirection makes use of the weapon's momentum. If you are at all unsure of your ability to deliver a block with speed and power, then you must concentrate on learning to redirect an oncoming attack.
In the absence of anything else, the 360 degree defence from krav maga is pretty easy to learn.
3. HitYou may have heard stories of boxers surviving knife attacks. Strange then, that knife defence videos seem to concentrate on applying locks. It's all the more strange when you consider the fine motor skills that are needed to apply a joint lock. All those pin sharp techniques you developed suddenly fly out of the window when a good dose of adrenaline hits your system. Boxers are no stranger to adrenaline, and know that their best chance is to use those powerful punches they have trained time and time again. Sure, it doesn't have the finesse of a perfectly executed joint lock, but that's the whole point. We are dealing with simple, brutal and effective here.
More to the point, simultaneous attack and defence is the key. If you're applying a block or redirection, it is advisable that it is accompanied with a strike of some kind. What about kicking them as they approach? You'll be lucky to get so much of a warning: the knife will usually be drawn when the attacker thinks you have the least chance of reacting. If your attacker is stupid enough to make it obvious that he is drawing a knife at such a long range, I would still caution against kicking. Half expect that your leg will be cut, affecting your mobility and, therefore, your chance of escape.
So, you've hit your attacker, possibly a few times. Should you apply a lock? Well, in the eyes of the law, if your opponent is stunned enough that you can apply a lock or throw, why did you not take advantage of this and escape? If you are skilled enough, and immune enough to the effects of adrenaline, to disarm him or her, fair enough. Otherwise, remaining with someone who is holding a blade and wants to use it is foolhardy in the extreme.
Summing upControl, manoeuvre and hit, control, manoeuvre and hit, control, manoeuvre and hit. As soon as a means of escape is available, take it. If you hit your opponent hard enough to dump them on the ground, then run. Never follow them to the ground: it puts you in a shaky position legally and you have lost the ability to easily escape. If they have an accomplice, and you go to the ground, you're probably dead.
Filipino martial artists say that any improvised weapons that are available should be used. I'll leave the legalities of this to one side and say that, from a practical standpoint, they're correct.
Always expect that you will get cut by a knife, and try to minimise the damage. As I said, not getting cut is unusual. Avoid being on the wrong end of a blade, if at all possible. Of all the rules I could possibly pass to you regarding knife attack survival, that one is by far the most important.