If you have every done any submission grappling, i.e. jiujitsu, sambo, or catch wrestling, you are hyper-aware of what planes your knee is supposed to function in. This is actually true for most people and most joints, regardless of grappling experience. Joints are meant to do certain tasks and when they perform different, or unnatural tasks, it usually hurts – except the heel hook. Why?
The dangers of the heel hook are so commonly known in grappling that we don’t even practice completing them on one another. All other techniques we encourage the person being submitted to feel and understand how much opposition they can put forth, before their joints go pop, or they pass out. It becomes *painfully* obvious how far you should push yourself. Yet the heel hook does not follow this model. Most grapplers know this technique exists, but don’t know why they don’t feel the normal “hey you should probably tap signals.”” Most medical students, or physicians don’t know this technique exists, but could probably explain why you may permanently destroy your knee before you tap to a heel hook. This is where I will try to bridge the gap.
First let’s look at the mechanics of a heel hook:
You can see this man in the black rashguard using his elbow to cradle the shirtless guy’s heel and is forcing said heel to rotate outward and the toes to rotate in.
For the medical students reading this, the black rashguard guy is cradling the posteromedial portion of the shirtless man’s calcaneous and is performing a motion that would be similar to internal rotation of the knee. If you are medical student you may have caught that there is no such thing as internal rotation at the knee, especially if the hip is isolated (which does perform internal rotation for the thigh, leg and foot). That is how we perform the technique called the heel hook; by creating an unnatural internal rotation of the leg at the knee joint.
For the grapplers out there the reason why you feel pain is because you receive pain information from different receptors in your muscles and tendons:
- stretch receptors – tell you how far your muscle is stretching in space
- and force receptors (when you exert force to resist an armbar, the receptors that make your muscle give up before your opponent snaps you arm are technically called golgi tendon receptors).
These receptors and muscles run parallel to the joints they are crossing. As muscles are stretched from forced forced hyper-extension they transmit signals to tell you to stop whatever is happening to them.
This doesn’t happen during the heel hook because the muscles that act on the knee are not running in the same axis as the motion the knee is (unnaturally undergoing). What do I mean by that?
The knee is what is referred to as a pure hinge joint meaning it undergoes strictly flexion (red arrow facing right) and extension (red arrow facing right) of the lower leg. The blue arrows represent rotation of the lower leg bones, the tibia and fibula around the hinge joint axis, which as you can clearly see is not something it is supposed to do. This differs than say an armbar, or a kneebar, which would simply hyper extend the joint.
The armbar or kneebar hyper extension would exert a high tension force on the muscles of the knee, creating the pain signals formerly discussed. When you rotate the knee about this axis, very little stretch will occur before you tear you cruciate ligaments (ACL, PCL etc.circled in red) and lateral collateral ligaments (circled in black) enough to change your knee forever.
So, my grappling friends remember, tap early and tap often. And to my medical student friends, tell your future patients to not be a tough guy and tap to heel hooks.