Knees are one of the most common areas of injury in BJJ. With the popularity of nogi Jiu Jitsu and leg entanglements, attacks to the knee are common.
The knee is commonly thought of as a hinge joint, meaning it only moves front to back like a hinge. Yet, the knee also has both internal and external rotation of the tibiofemoral joint (the meeting of the tibia and the femur) associated with its biomechanics.
The knee has numerous restraints to movement:
1. ACL- Primarily restrains forward movement of the tibia & acts as a secondary stabilizer against the internal rotation of the tibia and valgus angulation at the knee
2. PCL- The primary function of the PCL is to resist posterior translation of the tibia on the femur at all positions of knee flexion. It is a secondary stabilizer against the external rotation of the tibia and excessive varus or valgus angulation at the knee.
3- MCL- The functions of the superficial and deep MCL differ. The superficial MCL functions as the main contributor in preventing valgus displacement of the knee and works in conjunction with the ACL in preventing anterior translation and internal rotation. The deep MCL functions as a meniscus stabilizer and helps stabilize internal rotation of the knee from full extension through 90 degrees flexion.
4. LCL- The LCL functions as the primary stabilizer to prevent varus angulation of the knee.
GOAL OF THE HEEL HOOK
The goal of the heel hook is to isolate and stabilize the femur while rotating the bottom segment at the heel.
Here is where the difference between the inside heel hook and the outside heel hook differ.
The foot/ ankle also have inside and outside restraints to rotation. Though outside of the scope of this post, the outside ankle ligaments are smaller and allow greater movement than the thick Deltoid ligament on the inside of the ankle.
Because of this, the inside heel hook allows less movement at the ankle and thus translating the rotation directly up the leg and into the knee/ tibiofemoral joint. With the femur already isolated and stabilized, the ligaments are maximally stressed and often ruptured due to the lack of sensory receptors muscles and tendons have.
Hassebrock, J. D., Gulbrandsen, M. T., Asprey, W. L., Makovicka, J. L., & Chhabra, A. (2020). Knee Ligament Anatomy and Biomechanics. Sports Medicine and Arthroscopy Review, 28(3), 80–86. doi:10.1097/jsa.000000000000027
Zhang, L., Liu, G., Han, B., Wang, Z., Yan, Y., Ma, J., & Wei, P. (2020). Knee Joint Biomechanics in Physiological Conditions and How Pathologies Can Affect It: A Systematic Review. Applied bionics and biomechanics, 2020, 7451683. https://doi.org/10.1155/2020/7451683
