![]() The humerus rotates in the same direction in each case, regardless of the position of the elbow, forearm, or hand. Internal rotation with the arm in a position of 90° of abduction or 90° of flexion uses the same concept. For example, when viewing a right shoulder from the superior to inferior direction, a counterclockwise rotation of the humerus would be referred to as internal rotation (Fig. Internal rotation describes motion around a center of rotation such that the angular motion vector points towards the midline. For this reason, appropriate glenohumeral and scapulothoracic resting positions should be utilized such that accurate assessment can be achieved (the scapular plane and the glenohumeral resting positions are discussed in more detail below). Thus, any evaluation of the capsular structures may produce inaccurate results when the humerus is abducted in the coronal plane. For example, examination of the patient with straight lateral abduction of the shoulder would place an increased stress on anterior structures relative to posterior structures (Fig. This slight forward angulation facilitates examination such that surrounding soft tissues are similarly lax on both the anterior and posterior sides of the joint. ![]() This position should be differentiated from abduction within the scapular plane which places the humerus in approximately 20–30° of forward angulation, also termed “scaption” (Fig. Abduction of the shoulder occurs when the humerus is elevated in the coronal plane such that the extremity points directly laterally (also known as straight lateral abduction) (Fig. ![]()
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