Dance Anatomy & Kinesiology

386 Dance Anatomy and Kinesiology

Infraspinatus and Teres Minor

The infraspinatus and teres minor are functionally aligned muscles located on the back of the scapula

(figure 7.12). As its name implies, the infraspinatus (infra, below) runs from below the spine of the

scapula (medial infraspinatus fossa) laterally and upward to attach onto the posterior aspect of the

greater tubercle on the back of the humerus. The teres minor (teres, round + minor, lesser) runs from

the inferolateral border of the scapula to attach just below the infraspinatus on the greater tubercle and on

the adjacent shaft of the humerus. As with the supraspinatus, the tendons of these muscles are adherent

with the shoulder capsule and are important for preventing dislocation of the shoulder. These muscles

produce external rotation and horizontal abduction of the shoulder. They also participate in the SIT force

couple, a force couple vital for proper shoulder mechanics that is discussed later in this chapter.

Palpation: While sitting in a chair, lean your torso forward about 30° and place the fingers of your

left hand just to the outside of the lateral margin of the right scapula while your right arm is hanging

straight down toward the floor. The infraspinatus and teres minor can be palpated when the arm is slowly

externally rotated in this position. The infraspinatus can be felt contracting just below the lateral portion

of the spine of the scapula. The teres minor can be felt contracting just below the infraspinatus.

Attachments and Primary Actions of Infraspinatus and Teres Minor

Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)

Infraspinatus

(in-frah-spi-NAH-tus)

Medial portion of

infraspinous fossa of

scapula

Middle of greater tubercle

of humerus

Shoulder external rotation

Stabilization of shoulder

Shoulder horizontal abduction

Component of SIT force couple

Teres minor

(TE-reez MY-nor)

Dorsal aspect of lateral

border of scapula

Lower greater tubercle and

adjacent shaft of humerus

Same as infraspinatus

Subscapularis

As its name suggests, the subscapularis (sub, under

+ scapular, scapula) is located deep to the scapula

(figure 7.13). The subscapularis courses from its

attachment on the costal surface of the scapula later-

ally, upward, and slightly forward to attach onto the

lesser tubercle of the humerus. This more anterior

attachment on the humerus allows the subscapularis

to function as an internal rotator of the humerus and

to help prevent anterior subluxation or dislocation

of the humerus. This muscle can also help prevent

inferior dislocation of the shoulder. Due to the slope

of the glenoid cavity, downward dislocation of the

humerus requires lateral movement of the head of

the humerus, which can be prevented by muscles

with a horizontal line of pull including the subscapu-

laris, infraspinatus, and teres minor (Hamilton and

Luttgens, 2002). In addition, the subscapularis plays

a part in the SIT force couple.

Attachments and Primary Actions of Subscapularis

Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)

Subscapularis

(sub-scap-u-LAR-is)

Costal surface of scapula

(subscapular fossa)

Lesser tubercle of humerus Shoulder internal rotation

Stabilization of shoulder

Component of SIT force couple

FIGURE 7.13 Anterior view of rotator cuff muscles:

subscapularis and supraspinatus (right shoulder, deep

view of costal surface of scapula).