Scapulohumeral Rhythm
The shoulder joint is a complex joint with the most mobility in the body. This joint is commonly known for being made up of the glenoid fossa and the head of the humerus, but what is not commonly known is the profound effect the surrounding structures have on the motions of the shoulder.
Specifically, the scapulohumeral rhythm is extremely important for upper extremity movement. This is the interconnected distribution of movement between the scapula and humerus that allows for full ROM at the GH joint. For roughly every 3° of shoulder movement, the scapula moves 1° at the ST joint and the humerus moves 2° at the GH joint. Because of this relationship, if the scapula has limited ROM, then the shoulder will also have limited ROM. For example, if the scapula cannot upwardly rotate or posteriorly tilt, then motions that occur above the head are extremely limited. Motions like these, shoulder elevation, flexion, and abduction, are imperative for daily occupations, like reaching up to grab something from the top shelf of your pantry or scratching the top of your head.
It's weird to think that arm movement can be effected by the scapula, which in most people's minds has nothing to do with the shoulder. Another example of this relationship is, if the scapula cannot laterally rotate, then the head of the humerus will not be able to laterally rotate in order to move the greater tubercle of out of the way to reach full shoulder abduction.
Scapulohumeral rhythm ensures congruency between the glenoid fossa and head of the humerus, and it is this congruency that permits an optimal length- tension relationship of the shoulder abductor muscles. If the congruency of of the GH joint is disrupted, the muscles functional ability around joint will be compromised and ROM will be decreased. As well as ensuring mechanical efficiency at the shoulder, the congruency of the GH joint also prevents impingement of the subacromial space located in between the acromion process of the scapula and the GH joint. Impingement of this area is damaging to the joint capsule, surrounding muscles, and bursa. This not only decreases ROM at the shoulder, but is very painful as well.
Specifically, the scapulohumeral rhythm is extremely important for upper extremity movement. This is the interconnected distribution of movement between the scapula and humerus that allows for full ROM at the GH joint. For roughly every 3° of shoulder movement, the scapula moves 1° at the ST joint and the humerus moves 2° at the GH joint. Because of this relationship, if the scapula has limited ROM, then the shoulder will also have limited ROM. For example, if the scapula cannot upwardly rotate or posteriorly tilt, then motions that occur above the head are extremely limited. Motions like these, shoulder elevation, flexion, and abduction, are imperative for daily occupations, like reaching up to grab something from the top shelf of your pantry or scratching the top of your head.
It's weird to think that arm movement can be effected by the scapula, which in most people's minds has nothing to do with the shoulder. Another example of this relationship is, if the scapula cannot laterally rotate, then the head of the humerus will not be able to laterally rotate in order to move the greater tubercle of out of the way to reach full shoulder abduction.
Scapulohumeral rhythm ensures congruency between the glenoid fossa and head of the humerus, and it is this congruency that permits an optimal length- tension relationship of the shoulder abductor muscles. If the congruency of of the GH joint is disrupted, the muscles functional ability around joint will be compromised and ROM will be decreased. As well as ensuring mechanical efficiency at the shoulder, the congruency of the GH joint also prevents impingement of the subacromial space located in between the acromion process of the scapula and the GH joint. Impingement of this area is damaging to the joint capsule, surrounding muscles, and bursa. This not only decreases ROM at the shoulder, but is very painful as well.
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