Scapulohumeral Rhythm
Scapulohumeral rhythm may be a term that sounds fancy or like it would be too hard to understand, but it really just describes the relationship between the movement of the scapula (shoulder blade) and the humerus (arm proper). Essentially, as the humerus abducts, the scapula rotates upwardly as well. Clinically, scapulohumeral rhythm has many reasons that it is relevant. One reason is that it helps to ensure that the head of the humerus stays aligned with the glenoid fossa. This means that the head of the humerus has a surface to roll and glide on. Another reason that scapulohumeral rhythm is relevant is that it helps to maintain an optimal length-tension relationship. If the scapula was not able to move, the deltoid muscle would shorten to a point in which it could not shorten any more before the arm reached 180°. Because the scapula contributes to some of the range of motion, the deltoid is able to maintain its ability to contract through a longer range of motion. Yet anot...