270 THE ARTICULATIONS OR JOINTS. 
ligaments are three in number, and occupy the following positions: the superior is placed above the 
aperture in the front of the capsule ; the middle and inferior on the antero-inferior aspect of the 
capsule, and below the aperture mentioned. 
The superior gleno-humeral ligament, which some believe to represent the ligamentum teres 
of the hip-joint, springs, along with the middle gleno-humeral band, from the upper part of the 
anterior glenoid margin. The inferior band is the strongest of the three, and springs from the 
lower part of the anterior glenoid margin. 
Intra-capsular Structures.—1. The glenoid ligament, already described. 2. 
The long tendon of the biceps passes outwards from its attachment to the apex of 
the glenoid fossa and the adjoining part of the glenoid ligament, above the head and 
neck of the humerus, to escape from the interior of the capsule by the opening 
between the tuberosities of the humerus, subjacent to the transverse humeral 
ligament. 
Synovial membrane (Fig. 210) lines the capsule of the joint, and extends from 
the margin of the glenoid fossa to the humeral attachments of the capsule, where it 
is reflected towards the 
margin of the articular 
cartilage. It is there- 
fore important to note 
Long head 
of biceps in 
its tubular 
sheath of 
: Long head 
synovial 
of biceps 
ep Eaue that the inferior aspect 
of the humeral neck has 
the most extensive 
Head of clothing of synovial 
Head of _} scapula membrane. Further 
humerus 2 
the synovial membrane 
envelops the intra-cap- 
sular part of the tendon 
of the biceps, and al- 
though this tubular 
sheath is prolonged upon 
the tendon into the 
upper part of the bi- 
cipital groove, yet the 
closed character of the 
synovial cavity is main- 
tained. Thus, while the 
Fic, 210.—VERTICAL SECTION THROUGH THE SHOULDER-JOINT. tendon 1S within the 
capsule, it is not within 
the synovial cavity. The synovial membrane is continuous with those burs 
which communicate with the joint cavity through openings in the ligamentous 
capsule. 
io 
I iff 
L 
Burse (a) Communicating with the Joint Cavity—Practically there is only one bursa which 
is constant in its position, viz. the subscapular, between the capsule and the tendon of the sub- 
scapularis muscle. It varies considerably in its dimensions, but its lining membrane is always 
continuous with that which lines the capsule (Figs. 207 and 208), and therefore it may be 
regarded merely as a prolongation of the articular synovial membrane. Occasionally a similar 
but smaller bursa occurs between the capsule and the tendon of the infraspinatus muscle. 
(b) Not communicating with the Joint Cavity.—The sub-deltoid or sub-acromial bursa is 
situated between the muscles on the superior aspect of the shoulder-joint on the one hand and 
the deltoid muscle on the other. It is an extensive bursa, and is prolonged subjacent to the 
acromion process and the coraco-acromial ligament. It does not communicate with the shoulder- 
joint, but it greatly facilitates the movements of the upper end of the humerus against the under 
surface of the coraco-acromial arch. 
Movements at the Shoulder-Joint.—A ball-and-socket joint permits of a great variety of 
movements, practically in all directions ; but if these movements be analysed, it will be seen that 
they resolve themselves into movements about three primary axes at right angles to each other, 
or about axes which are the possible combinations of the primary ones. 
Thus, about a transverse axis, the limb may move forwards (flexion) or backwards (extension). 
About an antero-posterior axis it may move outwards, 7.e. away from the mesial plane of the 
trunk (abduction), or inwards, 7.e. towards, and to some extent up to, the mesial plane 
(adduction). 
About a vertical axis, the humerus may rotate upon its axis in an inward or outward direction 
to the extent of a quarter of a circle. 
