2. It is a synovial joint of ball and socket type.
Articular structures:
- Glenoid cavity of scapula
- Head of humerus.
3. Structurally, it is a weak joint because the
glenoid cavity is too small and shallow to
hold the head of the humerus in place.
However, this arrangement permits great
mobility. Stability of the joint is maintained
by:
- Coracoacromial arch
- Musculotendinous cuff of the shoulder
- Glenoidal labrum.
- Atmospheric pressure
4. Ligaments
Capsular ligament: it is very loose
and permits free movements and is
least supported inferiorly where
dislocations are common.
- medially, the capsule is attached to
the scapula beyond the supraglenoid
tubercle and the margins of the labrum
- Laterally, it is attached to the
anatomical neck of the humerus but
with few exceptions.
5. - anteriorly, the capsule is reinforced by
supplemental bands called superior, middle
and inferior glenohumeral ligaments.
Coracohumeral ligament: it extends from
the root of the coracoid process to the neck
of the humerus opposite the greater tubercle.
It gives strength to the capsule.
Transverse humeral ligament: it bridges the
upper part of the bicipital groove.
The glenoidal labrum: it is a
fibrocartilaginous rim which covers the
margins of the glenoid cavity, thus increasing
the depth of the cavity.
6.
7. Relations
Superiorly: coracoacromial arch,
subacromial bursa, supraspinatus and
deltoid.
Inferiorly: long head of the triceps brachii,
axillary nerves and posterior circumflex
humeral artery
Anteriorly: subscapularis,
coracobrachialis, short head of biceps
brachii and deltoid
Posteriorly: infraspinatus, teres minor and
deltoid
Within the joint: tendon of long head of
