There is still aproximately a 30% chance that you might encounter a knife in the hands of an attacker according to the UCR trends over the past 5 years. It's important to understand the rules of the knife attack long before you find yourself involved in one. So let's break down a few that I've encountered and trained on first-hand.
1. Expect to be cut. During any edged weapon attack there is a possibility that you will be cut, so you should expect that to happen and train to limit or avoid it at all costs. Unless the edged weapon has a full grip handguard it is also likely that the attacker will wind up with a cut hand if the knife shifts during a stabbing motion.
2. Trained individuals with a knife are more difficult to handle. In some instances it will be obvious that a person is trained in using an edged weapon, but for the most part it will be difficult to know.
3. Disarming a knife attack is not an impossibility. It's not always going to be easy and the technique used will always depend up on where the attacker is positioned in relation to the victim as well as the proximity to the victim.
4. You must remain calm. Remain calm, it will help keep your heart rate, breathing rate, and adrenaline under more control than if you simply let the fight or flight reactoin take over. Fine motor skills such as the use of your fingers drops off as heart rate increases, brain function becomes streamlined as breathing rates spike, and spikes in adrenaline heighten the survival mode of the body, often blocking the brain from thinking clearly.
5. Attackers are typically worried about movements. The typical response to a frontal attack at a slight distance is to put up your hands in the surrender position. Since this is a normal reaction for many, use it to your advantage. Avoid raising your hands up high, keep them just above shoulder level (hands only, so the elbows are low) or directly in front of your shoulders. Utilize a forward waving motion with the forearm and hand while verbally communicating your panic and confusion (stay calm). If you're trained in knife disarming this can give you the opportunity to disarm as the attacker is more likely to begin focusing on your moving arms rather than the knife in their own hands.
6. Proximity (distance) effects the knife attack. Proximity can be very dangerous with any edged weapon. The closer your attacker is, the more limited the type of edged weapon attack will be. For example, if your attacker is witihin a single arm's reach (you reach out and you can touch them) the full arm slice is a bit difficult to perform without the victim being warned by large body movement that it is about to occur. It can force the attacker to perform a forward stab with full arm movement. The closer you can get in this type of situatoin the more limited the forward stab becomes. But it comes at a price because sensitive body parts will be in proximity of the edged weapon.
7. Going to the ground is deadly for the person that winds up on the bottom. Where proximity becomes the most dangerous is in the ground fight. If an attacker winds up on the ground for whatever reason and finds his or her way on top of the victim the situation can turn very deadly. The attacker then has the ability to slash, full arm stab, reach sensitive parts, and limit the victim's movements. When the roles are reversed (attacker on the bottom) the full arm stab is difficult unless the attacker can sit upright. The slash is difficult because the person on top can trap the arms limiting that attack. The attacker's own sensitive body parts are now at risk.
These are not the end all, be all of the edged weapon encounter. They are simply things I have encountered and trained upon personally. You must train on how to open the door to get to your firearm in up close and personal situatoins as well as how to take accurate shots at that same distance. It's unconventional to say the least, but it's very effective.