Biomechanics: Joint locks Biomechanics: Positional

Understanding Shoulder Locks

The shoulder, or glenohumeral joint, is the most mobile joint in the human body which may explain why it is an ideal joint to attack for offensive joint locks. There are a variety of submissions that attack the vulnerable joint: kimura, americana and omoplata. It is crucial to understand the kinesiology of the shoulder joint to understand how each joint lock affects the shoulder.

Kinesiology of the shoulder joint
Motion at the shoulder is complex because it is a joint that has 3 degrees of freedom: meaning it can move in each place of motion: sagittal, frontal and transverse. The prime movers of the shoulder, deltoids, will assist with shoulder elevation while other muscles and structures will stabilize the humeral head in the glenoid fossa. Without proper stabilization the shoulder’s ability to move will be impaired.

Shoulder stabilizers:
1. Labrum: The glenoid fossa is a fairly small area, so the humeral head does not have a secure connection, however the glenoid labrum is a structure that depends the glenohumeral joint and helps to reinforce the joint.
2. Joint Capsule: The joint capsule is connective tissue that surrounds the joint. The axillary pouch is a structures that helps to reinforce the joint.
3. Ligaments: There are several ligaments that help to add static stabilization: glenohumeral joint ligament.
4. Rotator cuff: The rotator cuff is a collection of 4 muscles whose job is primarily to help stabilize the humeral head in the glenoid fossa while humeral elevation occurs. The four muscles: supraspinatus, subscapularis, infraspinatus and teres minor.
These are primarily the structures the joint locks target while attacking the shoulder.

Differentiating shoulder locks:

The Americana is rumored to have gained its name because big strong american catch wrestlers had early success with this technique. This submission functions by imparting excessive external rotation on the shoulder. A typical person only have 90 degrees of shoulder external rotation. In addition to excessive motion a properly executed americana also applies a shear force to anterior translate the glenohumeral joint in the glenoid fossa. This motion is common for anterior shoulder dislocations.

The rotator cuff muscles help to stabilize the humeral head in the glenoid fossa with the subscapularis being the primary dynamic constraint that is resists excessive external rotation. The static structures that oppose this motion are anterior band of the inferior glenohumeral ligament, axillary pouch and the middle glenohumeral joint ligament. A forceful anterior translation may also fray or tear the glenoid labrum. Glenohumeral capsule laxity can also occur from repeated stretching of these structures, such as years of late tapping to this shoulder lock.


The kimura or the “double wrist lock” is one of the most powerful submissions in grappling. The submission became famous when Masahiko Kimura used it to defeat Helio Gracie in a grappling match.
The kimura submission primarily attacks the shoulder joint by forcing excessive internal rotation of the shoulder. A typical person has 50-70 degrees of internal rotation.

The rotator cuff muscles help to stabilize the humeral head in the glenoid fossa with the infraspinatus being the primary dynamic constraint that is resists excessive internal rotation. The static structures that oppose this motion are anterior band of the inferior glenohumeral ligament, axillary pouch and the middle glenohumeral joint ligament.


This submission attack is Portuguese for “Shoulder blade”. While the submission attack involves using your legs to challenge the shoulder the mechanics are the same as the kimura.

How to make your shoulder locks more efficient:
1) The job of the rotator cuff is to stabilize the humeral head in the glenoid fossa while the prime movers move the arm. The rotator cuff muscles are at their weakest when the shoulder is abducted to 90 degrees. The supraspinatus is at a mechanical disadvantage to stabilize and the infraspinatus/teres minor have poor muscle activation at this position. Therefore if the rotator cuff muscles are the dynamic constraints they will be inefficient for resisting this excessive motion.
2) If the average person only have 50-70 degrees of internal rotation / 90 degrees of external rotation then why can some people move much further? Compensation. When applying the submission they take off too much weight attempting to ‘crank’ the arm. This allows other parts of the body to move: thoracic rotation, scapular rotation or elbow flexion. So while they are applying force what they are really doing is bleeding energy and being inefficient with their movements. Isolate their motion to the glenohumeral joint and minimize their back elevating from the ground.
3) To ensure you are attacking the glenohumeral joint with your movement make sure to keep the elbow bent at 90 degrees. This allow you to use the wrist control as a lever to focus energy on your intended target, the shoulder, instead of your energy going into the humerus bone or the elbow.

Shoulder locks? Why did my elbow pop?
As I discussed the kimura primarily attacks the shoulder by causing excessive internal rotation. However other structures can be affected with faulty mechanics.

Example 1- Sakuraba vs Renzo Gracie. At the end of the match Renzo had a body lock which allowed Sakuraba to lock in the kimura grip. A scramble ensued where Sakuraba was able to reverse the position. Due to the loss of ground contact Renzo was able to maneuver his arm to reduce the stress on his shoulder. Once they hit the ground Saku attempting to internally rotate the shoulder instead put a varus force into the elbow which dislocated the humerus from the ulna.

Example 2 – Frank Mir vs Nogueria II. Mir was able to lock on a kimura grip after a ground battle was initiated. In this situation Mir has Nog’s shoulder at a lower angle, less then 90 degrees. This shoulder angle does not put the rotator cuff muscles in a mechanical disadvantage and were able to stabilize joint. Because the shoulder was not isolated the force was transferred to the humerus, which caused a fracture of the bone.

Kimura : submission or control?
Grappling is a collection of movements that allow a practitioner to use superior leverage and body mechanics to control and disable an opponent, and one unorthodox method of control is the kimura grip. Instead of using gravity and body positioning to control an opponent the attacker can manipulate the arm in such a way that they will willingly concede their advance.

Kinesiology of the grip: The shoulder is weakest at 90 degrees of shoulder abduction. Not only are many of the glenohumeral ligaments taut but also the rotator cuff muscles are at a mechanical disadvantage to perform their job, which is stabilizing the humeral head in the glenoid fossa. What does all this mean? The opponent has to address the control position to avoid stress on their weakened shoulder joint. This control allows the attacker to move the defender or holds the defender in place so that the attacker can move around the defender.

This control position gained attention when famous Japanese fighter, Kazushi Sakuraba, saw success with this unorthodox technique. The grip is often used to counter techniques, such as rear body lock takedowns, single leg takedowns and/or guard passes.

Control does not have to be positional dominance but can also be by exploiting weak points in human anatomy.

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