When performing a straight ankle lock the specific joint attacked is the talocrural joint. The talocrural joint connects the shin (tibia/fibula) to the foot (talus). The talocrural joint has 1 degree of freedom, meaning it can only move in one plane – up and down (dorsiflexion and plantarflexion). When someone is attempting the straight ankle lock they are attempting to force the ankle into excessive plantarflexion. Excessive plantarflexion is resisted by the anterior talofibular ligament (outside ankle ligament), deltoid ligament (inside ankle ligament), the joint capsule (connective tissue surrounding the joint) and the muscles responsible for the opposing motion, such as the tibialis anterior.
This is where the submission is often finished incorrectly. Many beginners will try to “stretch” the foot into this range, however there are so many structures to resist end-range plantarflexion it often is a very difficult finish. This may cause pain, but to inflict damage you have to impose a significant amount of force. Ever roll with someone who has ‘flexible feet’ and no matter how much you try to stretch their foot they won’t tap?
As the foot moves into plantarflexion the talus slides forward and at end-range only the most narrow width of the talus connects to the tibia/fibula. Due to the loosening of the grip the joint becomes unstable against further anterior forces. This means that if your goal is to disable your opponent / inflict damage you need to bring the ankle to its end-range THEN introduce an anterior force to dislocate the joint.
An example of this leg lock finished correctly was when Shinya Aoki fought Tatsuya Kawajiri. Kawajiri attempted to ‘tough out’ the submission until his ankle dislocated.
Difference between an ankle lock and achilles compression?
A variation on the straight ankle lock is the achilles tendon compression. When dealing with someone who has adequate ankle mobility this variation may elicit a quicker tap compared to the standard ankle lock. Prior to applying a compressive force you want to bring the ankle to end-range plantarflexion so that the tendon has the maximum possible tension. To finish this variation you use the styloid process of the radius (bony prominence on the end of the forearm/wrist) to compress the tendon at near the base of the calcaneous. The forearm acts as a fulcrum by using the ankle for leverage. The perpendicular shear force introduced by the bone onto the maximally taut tendon will force even people with “flexible feet” to tap.
The advantage of using a move like this is that it targets a musculoskeletal structure that is highly innervated. Often when grappling an opponent ignorant of leg locks they will respond too late and by the time they tap damage already occurred. This variation will get the desired response regardless of their knowledge of lower extremity submissions.
1. Martin, R. L., Davenport, T. E., Paulseth, S., Wukich, D. K., Godges, J. J., Altman, R. D., … & MacDermid, J. (2013). Ankle stability and movement coordination impairments: ankle ligament sprains: 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, 43(9), A1-A40.
2. Neumann, D. A. Kinesiology of the Musculoskeletal System: Foundations for rehabilitation. 2010. Mosby Elsevier.