Biomechanics: Joint locks Leglocks

Understanding Heel Hooks

Arguably the most damaging submission hold across all grappling styles, the heel hook works by isolating your opponent’s femur and rotating the tibia beyond its normal range of motion. In addition to attacking the ligaments in the knee, certain variations of the heel hook also attack the ligaments in the ankle.

Biomechanics of the heel hook:
The knee (tibiofemoral joint) has 2 degrees of freedom: sagittal plane motion and transverse plane motion. This means that the knee is able to not only bend and straighten, but rotate as well. The tibiofemoral joint allows up to 40-50 degrees of total axial rotation with a 2:1 ratio of external rotation to internal rotation. The primary constraints that stop excessive axial rotation are the ligaments that connect the two bones.

The ligaments that work to prevent this rotation include the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), the lateral collateral ligament (LCL). Posterior Lateral Corner (PLC)(Popliteofibular ligament, arcuate ligament-fabellofibular ligament).

The Role of the Meniscus: The menisci is essentially a pad between femur and the tibia which primarily distributes stress across the knee and absorbs force during weight bearing. The meniscus also has a secondary function of stabilizing the knee particularly with resisting hyperextension. Forceful twisting of the knee may damage the meniscus.

There are 3 reasons that this technique is so devastating:
1) Ligaments do not have the same sensory receptors that muscles/tendons do, so by the time tension is felt, there is a very small window of opportunity to tap.

2) Ligaments, the structures being attacked, do not heal as easily as other tissues in the body. Often these ligaments require surgical intervention to repair: the ACL, in particular. Rehabilitation of ACL reconstruction is very long in duration, often lasting 6 to 12 months before someone is cleared to return to sport.

3) Many grapplers are ignorant of the technique and do not respond properly when being attacked by this submission. Often the ignorant or inexperienced grappler will tap too late or attempt to escape by spinning without control, which may accidentally cause excessive tibial rotation and result in injury.

Mechanics of how to apply a heel hook:
1. Isolate the lower leg by squeezing the femur with both of your legs.
2. Put the opponent’s toes in your armpit.
3. Connect to the opponent’s heel to use as your fulcrum to apply torque.
Two options for the finish.
3A. Rotate the tibia: this primarily stresses the ligaments in the knee.
3B. Rotate the foot: this primarily stresses the ligaments in the ankle.

Why is this information important for a grappler to know?
1. For optimal finishing mechanics, you should know enough joint anatomy in order to maximize the effectiveness of the lock. This also allows you to troubleshoot, if you find that finishing the submission is difficult.

2. You should know what kind of damage you are about to do to your opponent/training partner, especially in the context of your training. Competition is one thing, but if your training partner isn’t tapping, consider letting it go rather than crippling them.

Heel hook: outside vs. inside
The inside heel hook is commonly seen as the more dangerous variation, but why? The heel hook submission works by locking down the femur and rotating the tibia. The ligaments of the knee are responsible for preventing excessive tibial rotation. The tibiofemoral joint typically has a 2:1 ratio of external rotation to internal rotation, meaning that the tibia can externally rotate more than it can internally rotate. So shouldn’t the the outside heel hook be more dangerous?

The outside heel hook is applied by contacting the heel to rotate the tibia, but often the resulting movement isn’t isolated to the tibiofemoral joint, but also involves the ankle. The ankle complex has 3 joints: talocrural, subtalar and midtarsal. When performing tibial internal rotation, subtalar inversion at the ankle also occurs. The outside ankle ligaments: anterior talofibular ligament (ATFL), posterior talofibular ligament (PTFL) and calcaneofibular ligament (CFL) are the primary structures that resist ankle inversion. When attacking with an outside heel hook, it is not uncommon for these ligaments of the ankle to be the first to fail, before force is transferred to the knee. These are the same ankle ligaments that are involved in a toehold submission or an inversion ankle sprain.

Now let’s look at the inside heel hook. The subtalar joint has 2:1 ratio of inversion to eversion, so there will be far less motion at the ankle when applying an inside heel hook. The deltoid ligament, which is responsible for preventing subtalar ankle eversion, is a very thick structure. The deltoid ligament is unlikely to fail; more commonly, the ligament will rip off part of the bone before it ruptures (avulsion fracture). Damage to the ligaments of the knee will likely occur before any ligamentous failure or fracture at the ankle, because the medial ankle ligament (deltoid ligament) is very strong and unlikely to rupture from the torque. So why is the inside heel hook more dangerous? The reason is that the mechanics involved in applying this variation isolate motion to the tibiofemoral joint of the knee, rather than splitting the force between the ankle and the knee. As a result, the inside heel hook is more likely to cause serious damage to the knee than the outside heel hook.

References:
1. Logerstedt, D. S., Snyder-Mackler, L., Ritter, R. C., Axe, M. J., & Godges, J. J. (2010). Knee stability and movement coordination impairments: knee ligament sprain: clinical practice guidelines linked to the international classification of functioning, disability, and health from the Orthopaedic Section of the American Physical Therapy Association. Journal of Orthopaedic & Sports Physical Therapy, 40(4), A1-A37.
2. Logerstedt, D. S., Snyder-Mackler, L., Ritter, R. C., Axe, M. J., Godges, J., Altman, R. D., … & Fearon, H. (2010). Knee pain and mobility impairments: meniscal and articular cartilage lesions: clinical practice guidelines linked to the international classification of functioning, disability, and health from the orthopaedic section of the American Physical Therapy Association. Journal of Orthopaedic & Sports Physical Therapy, 40(6), A1-597.
3. Neumann, D. A. Kinesiology of the Musculoskeletal System: Foundations for rehabilitation. 2010. Mosby Elsevier.

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