Dance Anatomy & Kinesiology

The Upper Extremity 379

the medial capsule that allow the arm to be raised to
the side and overhead. This looseness of the capsule
potentially allows 1 to 2 inches (2.5-5 centimeters)
of separation between the humerus and scapula
(Hamilton and Luttgens, 2002). However, despite its
limitations, the capsule is still vital for joint stability
(Warner et al., 1990).
The joint capsule is reinforced by various liga-
ments as seen in figure 7.7. Anteriorly, the capsule
is strengthened by the superior, middle, and infe-
rior glenohumeral ligaments. These ligaments help
prevent excessive displacement or translation of the
humerus, particularly in a forward direction. The
inferior glenohumeral ligament has been shown to
be a particularly key restraint for preventing anterior
translation of the head of the humerus in higher
ranges of shoulder abduction (Warner et al., 1990),
while the middle and superior glenohumeral liga-
ments resist anterior translation in lesser degrees of
abduction. The superior glenohumeral ligament is
also vital for preventing inferior translation of the
head of the humerus (Cavallo and Speer, 1998).
Superiorly, the capsule is reinforced by the
coracohumeral ligament (not shown). This ligament
runs from the base of the coracoid process into the
capsule to attach to the greater tubercle and lesser
tubercles of the humerus, helping to form a tunnel
between these tubercles within which the tendon of
the long head of the biceps brachii lies. A related
ligament, the coracoacromial ligament, spans
between the coracoid process and the acromion

process of the scapula to help form an arch above

the head of the humerus. This arch, composed of

the coracoid process, coracoacromial ligament, and

acromion process, is termed the coracoacromial arch

(Lyons and Orwin, 1998). The coracohumeral and

coracoacromial ligaments help prevent superior

dislocation of the humerus, and the latter can be

implicated in shoulder impingement. Classically,

shoulder impingement syndrome refers to a pinching

of soft tissues, such as the supraspinatus tendon or

subacromial bursa, between the head of the humerus

and the overlying coracoacromial arch.

Specialized Structures of the Shoulder Joint

Various specialized structures are associated with the

shoulder that provide additional joint stability and

aid with shoulder function. These structures include

the glenoid labrum and various bursae.

Glenoid Labrum

The glenoid labrum is a rim of fibrocartilage located

at the perimeter of the glenoid cavity (figure 7.7B),

functionally similar to the one found in the hip joint

(acetabular labrum). The glenoid labrum is thicker

around the circumference than centrally. It serves

to increase the size and depth of the glenoid cavity,

increasing the superior inferior diameter by 75%

and anterior-posterior diameter by 50% (Richards,

1999). In addition, the labrum provides a site for

attachments of the joint capsule, the glenohumeral

ligaments, and various tendons including the long

FIGURE 7.6 Movements of the shoulder joint. (A) Flexion-extension, (B) abduction-adduction and external rotation–

internal rotation, (C) horizontal abduction–horizontal adduction.

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