Knife Self-Defense: Biomechanical Cutting for De-Animation of the Opponent

I met Bram Frank at the 2013 BLADE show. The edged weapon self-defense expert was selling his CRMIPT knife. I bought two: the razor-sharp carry piece and a dull-edged trainer. I’ll report more on my progress with the concept (as above) as I go along. Meanwhile, Bram gave TTAK permission to republish his writing on the art of edged weapon self-defense. Here’s an article on “bio-mechanical cutting.” In other words, what to do when you’re defending your life with a knife . . .

Biomechanical cutting means to stop all mechanical function of the body. It does not mean to end or cease the functioning of the body or terminate its life. Street combat needs biomechanical cutting to achieve its ends while military combat needs to stop not only biomechanical function but in most cases termination of the unit in general. The goal of Biomechanical cutting in street combat is to stop a body’s mechanical function. If one stops the mechanical function of one’s opponent several things become clear in combative reality:

• The threat of attack is removed. If one’s opponent cannot make a physical action happen then the opponent’s desire or intent doesn’t matter

• The opponent’s mobility is gone. One’s escape can be implemented. The opponent cannot follow.

• The opponent’s condition is a deterrent to others wanting to take similar action

• Drugs, alcohol, lack of pain, great strength or other mitigating factors, which might help an opponent

in aggressive street combat, are negated and become moot.

• Legal ramifications are kept to a minimum: Death is hard to reconcile

The human body is basically a complex mechanical unit. There is a frame work, an interior structure that maintains form, and function with tissue that connects the pieces and connective tissues the extend or contract the pieces. There are fuel lines, lubricants, and a complex electrical system with on board computer hook up. By interfering with any of these systems, the mechanical unit shuts down. Cutting any of these connections, joints or electrical pathways damages the unit till it can be surgically repaired. Cutting is the imperative word here for percussive striking may or may not do damage.

One can suppose or speculate on percussive damage by theory or by inferred results but cutting is different. Every one cuts and bleeds. Steel cuts flesh. Severing living flesh and the working human mechanical system brings obvious results.

Humans are very easy to injure, maim, and destroy parts of rather than terminate. The human body and spirit are very resilient and that resiliency keeps people who should have died from their wounds alive and fighting. Emergency rooms are full of should have died patients. War heroes are given posthumous citations for somehow surviving an attack and then saving others and killing the enemy before expiring themselves.

This makes combat very complex! One could deliver a “death” blow and as one waits for one’s opponent to die, the opponent somehow manages to counterstrike and deliver his own death blow back at one. Tie score. Both die. This is an unacceptable combative solution.

In combat therefore, instead of looking to terminate the opponent with no biomechanical cessation of function, one should “destroy” the opponent’s operating system then terminate the opponent as the progression builds. In street combat that option does not exist. If one terminates an opponent one can end up in jail or in court or both. Therefore biomechanical cutting is of utmost importance in street combat.

Without terminating one’s opponent, one stops all possibility of threat or aggression by stopping the opponent from functioning. Just like the Black Knight in Monty Python’s Quest for the Holy Grail. The Black Knight has both arms and legs cut off by King Arthur and the hopping torso keeps yelling, “Come on! It’s only a flesh wound. Come closer so I can bite you!” King Arthur rides off into the sunset.

IMPORTANT: many people will gladly tell one that lethal force is allowed to be met with lethal force and “Don’t worry, In a court of law JUSTICE will prevail!” Only on paper, in certain circumstances, with certain people involved, is lethal force the accepted response to lethal force. Worse yet, those that would judge one for using lethal force, a jury of one’s peers, is NEVER of one’s peers and they are truly the common people with nothing in common with the one they judge.

If one’s opponent or opponent’s family doesn’t file criminal charges, the state may file criminal charges for one’s ethical self-defense actions that aren’t socially or legally acceptable. If one beats the criminal charges the same groups may file civil charges.

Biomechanical target zones: pulling the plug!

NOTE: Humans have a reflex of looking at our injuries. Humans go into some form of fetal position upon shock or injury: contraction rather than expansion. Intent does not count with biomechanical cutting. The opponent may have intent or the most will power in the world but function is function: if the

parts don’t work all the prayer, wishing or swearing will not make them work again until surgically repaired. This IS NOT AN ANATOMY LESSON. There are many more muscles involved than those mentioned. There are many nerves and circulatory vessels involved. This is to show WHY biomechanical cutting works at the SIMPLEST LEVEL to understand.

The fingers, hand and forearm:

The Filipino’s call it defanging the snake, or breaking the snake’s teeth, Sword-fighters of old called it “disarming” (literally!) and there are many cultures that used the concept of attack the attacking weapon. This is the first strike that one can apply to one’s opponent for the opponent willingly brings the weapon toward one’s defensive zone.

• Cutting the fingers of one’s opponent usually stops an attack. Fingers house lots of nerves, ligaments and tendons and if damaged, fingers cannot be used till they are surgically repaired. Fingers are no bigger than chicken legs and can easily be broken or cut off.

• Cutting the hand back or front can stop function. Cutting the back extensors can cause severe damage and bleeding and stops the fingers from opening. Cutting the front or palm of the hand will cut flexors causing severe damage and forces the hand to open. There is a lot of meat that can be cut including the opposing digit, the thumb.

Note: cutting the thumb can end the use of the hand immediately until the thumb is surgically repaired. Fingers don’t work well without an opposing digit to hold them in place.

The Forearm has many target areas unto itself and is an easy zone to reach.

• Cutting the muscles on the outside of the forearm cuts the extensors, which uncurl or extend the fingers. The nerve functions that control grasping are located on the outside as well. Catching a cut up by the elbow and pulling down toward the thumb can send a fillet over the opponent’s hand. The fillet may go down to the bone.

• Cutting the inside forearm contains the ateries and main nerves that control the wrist and the fist. Severing the nerves and /or the muscles will cause the flexors, which keep the hand closed not to work, or will destroy the needed nerve impulses to accomplish the same function. Fillets can be cut from the inside of the forearm as well as the outside forearm.

The middle arm: biceps and triceps are only big in the gym.

• The function of the biceps other than to look great is to pull the lower arm to the upper arm. Cutting either of the heads of the muscle, the belly of the muscle or picking pieces out of the biceps impairs the function. When the biceps don’t work, the arm will not contract or the lower forearm cannot be raised to an upright position. With the biceps cut or impaired it is easy to get an opponent to give the classic straight arm as used in arm bars or elbow breaks.

• The Triceps extend or straighten the arm. Cutting, picking pieces out of or impairing the triceps gives one an opponent with the lower arm contracted against the upper arm. This is the classic position for enacting the classic gooseneck locking.

The upper arm: shoulder; trapezium, deltoids and the chest

As one works one’s way up the arm it is easy to access the shoulders. Cutting the anterior Deltoid (the one that faces front) and the lateral deltoid (the one that makes shoulders look so good) stops the function of rotation of the arm as well as horizontal adduction of the arm. Cutting the back deltoid stops extension of the arm. The junction of the arm and torso has the connection of the chest or pectoral muscles.

The insertion point is the upper arm. Cutting these muscles at the junction stops adduction, horizontal adduction and rotation of that arm. Cutting the Trapeziums (the muscles that give one that powerful look from neck to shoulder) stops upward rotation of the arm as well as lifting of the arm.

NOTE: Working one’s way up the arm one could cut the deltoid or the external pectorals or even higher, one could cut the trapezium muscle to impair function. There is no need to cut the torso of the opponent. One might need to justify one’s cutting actions in a Court of Law before a Judge and Jury.

Everyone has cut a finger or a toe, most have gotten cut hands, and some have even gotten cut arms…people can relate to that. No one can relate to being stabbed, organs pierced, bellies cut open, throats slit, or testicles cut off. For bio-mechanical cutting one cuts limbs only and the cutting is to IMPAIR function not to inflict lethal injuries or de-animation of one’s opponent.

The legs and hips present another type but equally as good a target. Cut or impair the legs and /or the hips and mobility and balance are functionally stopped. This includes the Gluteus Maximus or as commonly known as the butt.

Professor Presas once asked me to kick at him. He told me kick VERY FAST. I hesitated but complied. He immediately struck my leg with a stick and laughed. I fell to the floor in great pain. “Oh Bram” he said “you kick a man with a weapon and you are now a gimp!” As I struggled to get up he told me to kick him again with the other leg. I was in pain, but I complied. The strike on my other leg dropped me upon impact.

“ You do not learn fast! Do you know what you are now!?” Before I could answer he shook his head and said, “ You are dead…NEVER kick at a man with a weapon. He will cut off your legs and then you cannot move or run away!”


While I was teaching an Edged weapon seminar in Europe, a master of Tae Kwon Do once told me he could kick a knife out of my hand BEFORE I cut him. I had him kick my hand, which I let go limp and my hand flew away and rebounded with the knife into his leg. He tried again only this time I moved my hand at the last minute and the kick missed and I drove the knife into his leg and up into his femoral region.

On his third attempt as his hip shifted slightly, I intercepted his motion. I drove the knife into the belly of his quadriceps and up into his flexor dropping him immediately in pain onto the floor. I told him and the other participants at my seminar that he was VERY lucky that I was only using a training knife otherwise he would be in serious trouble. No one tried kicking a knife out of anyone’s hands the rest of the seminar.

Before I start this section I need to state the obvious. Mobility is paramount in self-defense and in most physical situations. The quarterback of the Miami Dolphins, Dan Marino stepped back and popped his Achilles tendon. End of Marino’s mobility, BOOM onto the turf. Pick any Football, Soccer, Basketball or Baseball player that pops a leg muscle and see how well they move; they don’t move at all and get carried off the field.

These are tough, conditioned, PROFESSIONAL athletes and they drop like sacks of potatoes. Kick boxers routinely target the legs. Benny the Jet stopped many opponents with leg kicks and in the early days of the PKA-WKA many American fighter who ventured to fight overseas found out the hard way. Dead legs mean no mobility: End of fight.

Ever get a shot in one’s butt from lets say a nurse “Ratchet” and one cannot move one’s leg except in great pain with limited mobility? I have. On board ship, I was given a shot in my butt with a normal needle that felt like six inches long and I couldn’t walk for several days… Actually there were several of us on the ship in that condition. All from a tiny needle stuck INTO the Gluteus Maximus.

Legs: no legs no mobility

Cutting the legs of an opponent works. Most people do not expect to be cut or hurt in their legs. Cutting legs stops one’s mobility and ability to balance. The perfect attacker / opponent is one lying on the ground still screaming “ I’ll get you, come closer so I can grab you and I’ll get you” Ah, the infamous scene from Monty Python and the Holy Grail. King Arthur tries to go across a bridge and is challenged by the ultimate bad guy, the Black Knight. The Black Knight will not let King Arthur go by him to cross the bridge. They battle intensely.

Arthur cuts off the Black Knight’s arms and legs and this torso keeps screaming at King Arthur to come closer so that he can bite him. King Arthur shrugs his shoulders and “rides” away across the bridge. It works like that in real life as well except the torso will not be screaming for one to come closer so that it can bite one.

Upper Leg

Cutting, piercing, cutting pieces out of the opponent’s quadriceps (front) or hamstrings (back) immediately stop the action. Transitional cuts from arm to leg usually end up cutting the Sartorius. Cut the Sartorius and there is no pick up of the leg, no flexion, no abduction, and no lateral rotation. Ever pull an old style shade

and let it go? It rolls up very quickly. That’s what the Sartorius will do around the knee. Aim for the Sartorius and miss and one hits the flexors and abductors of the hips. Cut these muscles and the legs pivot outward just like de-boning a chicken. An opponent with no legs is in no better position to advance on one and attack or counter attack, than someone in a wheel chair. Ok, that’s wrong! A person in a wheelchair can have mobility and an opponent with non- functioning legs has NONE!

The Butt: great Glutes!

OK…it sounds very funny except when it’s your butt that got hurt. One of the largest muscle groups in the body is the Glutes. When the Glutes are incapacitated the body cannot move. Ask a football player who has torn a Glute. A hurt butt keeps him on the bench and off the field for many weeks. One needs the Glutes to be able to stand, move, walk, run and pivot. Poking the opponents butt with the tip of one’s knife can cause immediate stoppage of the opponent’s movement.

Tip ripping with the knife and popping a snow cone divot out of an opponent’s butt will end the confrontation. The opponent can still grab but the opponent cannot chase, run or stand. If that doesn’t finish the confrontation, then it can be a great opener to any other biomechanical cutting motion.

In a court of law, when it is pointed out by the attacker, that while in the act of attacking one, to mug, rape or rob, the attacker was hurt in his butt by the defender, (yes, see you’re smiling already!) the jury will be smiling because the situation seems funny. Again this is perception not reality but people in general have a hard time taking butt injuries seriously. Especially if it happens to the bad guy!

The Knee: a fragile hinged joint

The knee can take moderate amount of percussive abuse. Straight on the knee can absorb some impact, from the side the knee cannot take any substantial blunt trauma. Cutting the “knee” causes severe damage and bio-mechanically if the knee doesn’t work, the body stays in one place. The Quadriceps Femoris Group actually inserts below the knee and act to extend the knee joint. If any of them are cut the knee cannot bend nor can the hip flex.

The Rectus Femoris is a quad muscle that actually crosses both hip and knee. It is readily accessible to a direct cutting motion. The thick cords felt behind the knee are actually the end of the hamstrings and they control extension of the hip, flexion of the knee and rotation of the knee. Cutting through these muscles takes little effort and is as simple as removing a chicken leg from the thigh. Cut the connecting tissue and nothing is there. This is what old time “hamstringing’ was; the cutting of the hamstrings at the bend of the knee.

The calf: Gastrocnemius looks great, cuts easily

The Gastrocnemius or Gastro is Greek for “belly”. This muscle can act on the knee or the ankle separately but not simultaneously. A cutting of this muscle will totally immobilize an opponent till the muscle is surgically repaired. Ask Dan Marino. He stepped back to pass and the tendon ripped. No Achilles tendon, no movement. BOOM. All fall down!

The Foot: protected by the shoes

OK. So the opponent has shoes on, sneakers on (high tops no less), or boots. Stab right through the top of the shoe pinning the foot to the ground. Stab directly into the toes, injuring them or cutting them off. Ignore the foot and use the top edge of the sneaker or boot as a cutting guide and cut across the leg. What happens then? Go back and read the above section on calves. No feet, no movement, no mobility.

NOTE: I broke my big toe when I kicked someone in a combative situation. It was a “picture perfect” round kick to the opponent’s head. He dropped like a sack of potatoes. I dropped to my knees almost as fast. The pain was intense and I couldn’t move. I had broken off part of the joint of the big toe upon impact.

I once saw Professor Presas quick strip a stick from a student. It flew straight up in the air and came straight down, butt first directly onto Professor Presas’ big toe. He dropped to his knees in pain. Toe pain can bio-mechanically stop someone! Even someone as experienced as the Professor because he NEVER expected it.


  1. ChuckN says:

    Fantastic article. I’d love to train with him someday.

    I would like to add that while this method is less likely
    to cause death it can do so and relatively quickly
    depending on the area cut. If you cut the inside of the
    forearm to elbow, inside upper thigh, back of knee or a
    few of other points there is a chance in cutting into an
    artery,depending on depth and length. If this happens
    death can occur in seconds.

    Another point to think about is whether or not to go for
    the legs. Unless they present themselves as an easy target
    (in RF’s case a kick) attacking a leg can leave you in range
    of your opponent’s hands and/or weapons.

    A good way to minimize a second attack from your opponent
    is to either pin and immobilize, continue counter-attack until
    threat is neutralized, or after landing a debilitating cut
    protect and retreat.

  2. scubamatt says:

    He is simply describing the strikes from Modern Arnis, a well known form of FMA.

  3. Aharon says:

    Interesting tool. I suspect it is possibly effective when used by someone specifically well trained with crmipt along with a person who has accomplished a certain level and type of self defense training.

  4. Arod529 says:

    “Legal ramifications are kept to a minimum: Death is hard to reconcile”

    A very misleading (and entirely incorrect for some) statement.

    Deadly force legally means force that is reasonably likely to cause death or substantial bodily harm.

    My states penal code:

    “‘Substantial Bodily Harm’ defined. Unless the context otherwise requires, ‘substantial bodily harm’ means:
    1. Bodily injury which creates a substantial risk of death or which causes serious, permanent disfigurement or protracted loss or impairment of any bodily member or organ; or:
    2. Prolonged physical pain.”

    No matter what your intentions, you better damn well have a good reason to use that knife if you don’t want to be charged with Assault of a deadly weapon.

  5. steve says:

    Fantastic information. I appreciate the bio mechanic explanations. It’s one thing to know it’s a devastating blow, it’s another to understand what sort of damage is done.

  6. Don L says:

    I had the good fortune to train with GM Frank years ago at a Combat Hapkido Seminar. The information led me to study knife use and opened my eyes to the reality of knife combat. Outstanding info!

  7. Shane says:

    Good info. Nice to have some less lethal options in the toolbox. Lol. I never thought about cutting someones butt. That’s almost as affective as a kidney strike.

  8. Jefferson Santee says:

    Wow. Quick and to the point! Now I’m gonna get a mannequin and practice hitting all those points…both the cutting and stabbing. You’re upped my confidence a bit. Thank you…

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Knife Self-Defense: Biomechanical Cutting for De-Animation of the Opponent

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