10 下列旋轉袖（rotator cuff）肌肉中，何者能內旋手臂？

棘下肌（infraspinatus） 棘上肌（supraspinatus）

肩胛下肌（subscapularis） 小圓肌（teres minor）

answer is subscapularis

Muscles composing rotator cuff

Muscle	Origin on scapula	Attachment on humerus	Function	Innervation
Supraspinatus muscle	supraspinous fossa	superior and middle facet of the greater tuberosity	abducts the arm	Suprascapular nerve (C5)
Infraspinatus muscle	infraspinous fossa	middle facet of the greater tuberosity	externally rotates the arm	Suprascapular nerve (C5-C6)
Teres minor muscle	middle half of lateral border	inferior facet of the greater tuberosity	externally rotates the arm	Axillary nerve (C5)
Subscapularis muscle	subscapular fossa	lesser tuberosity (60%) or humeral neck(40%)	internally rotates thehumerus	Upper and Lower subscapular nerve (C5-C6)