The rotator cuff is a group of muscles forming a semicircle around the superior head of the humerus. Collectively, three of these muscles (subscapularis, infraspinatus, teres minor) along with the supraspinatus stabilize the head of the humerus while the middle deltoid and supraspinatus abduct the glenohumeral joint. Note that the middle deltoid alone is unable to initiate abduction; on the other hand, the supraspinatus is capable of performing the total motion of abduction without assistance from the deltoid (Brunnstrom, 1996). The anterior and posterior portions of the deltoid perform flexion/internal rotation and extension/external rotation of the glenohumeral joint, respectively. The muscles comprising the rotator cuff, along with their humeral attachments, may be noted as follows:
	1. Subscapularis -Lesser tuberosity
	2. Supraspinatus -Greater tuberosity -superior facet
	3. Infraspinatus -Greater tuberosity -middle facet
	4. Teres Minor -Greater tuberosity -inferior facet
To visualize the structural concept of the rotator cuff, place your thumb on the lesser tuberosity, and then allow the index, middle, and ring fingers to fall on the greater tuberosity. Your hand should be positioned medially opposite the humeral head. In this arrangement, your thumb should represent subscapularis, your index finger should represent supraspinatus, your middle finger should represent infraspinatus, and your ring finger should represent teres minor.
The learning device for remembering the muscles of the rotator cuff is by observing that the first letter of each muscle spells SITS. The muscles literally "sits" on the greater and lesser tuberosities of the humerus. Again, the muscles function importantly in stabilization of the glenohumeral joint during abduction; however, they function also in rotation of the humeral head within the glenoid cavity, as follows:
	1. Medial rotation:subscapularis
	2. Lateral rotation:infraspinatus, supraspinatus, teres minor

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