Shoulder Joint|Upper Limbs|Anatomy

 SHOULDER JOINT

CLASSIFICATION

Synovial joint of ball and socket type.

ARTICULAR SURFACES

They are formed by the large hemispherical head of humerus and shallow glenoid cavity of scapula.

The glenoid articular surface is deepened by the glenoid labrum.

Glenoid labrum

• It is a rim of fibrocartilage attached to the peripheral margin of the glenoid cavity.

• It is triangular in cross-section and deepens the shallow glenoid cavity.

LIGAMENTS

Capsular Ligament

• Attachments 

Medially-To peripheral margin of glenoid cavity outside the glenoid labrum. The supraglenoid tubercle is intracapsular.

Laterally-To anatomical neck of humerus except on medial side where it descends about 2-3 cm on the shaft, up to the surgical neck of humerus.

• Muscles strengthening the capsule

 In general, the capsule is loose and lax, but it is strengthened by the musculotendinous (rotator) cuff formed by the following muscles

 Supraspinatus-above

 Subscapularis-in front Infraspinatus

 Teres minor-Behind

• Openings in the capsule

The capsule presents two openings/deficiencies

One in front, for communicating with subscapular bursa 

One at the intertubercular sulcus to provide the passage for the tendon of long head of biceps brachii.

Transverse humeral ligament

This ligament bridges across the bicipital groove.

Glenohumeral ligaments

These are thickenings in the anterior part of the capsule and are seen when the capsule is exposed from the behind. They are three in number and named superior, middle and inferior glenohumeral ligaments according to their location.

Coracohumeral ligament 

It is a wide, strong fibrous band on the superior surface of the joint, extend- ing from the base of coracoid process to the anterior aspect of greater tubercle of humerus.

 Coracoacromial ligament

 It extends between the lateral side of coracoid process and the medial border of acromion.

RELATIONS

Superiorly

• Coracoacromial arch

• Subacromial bursa

• Supraspinatus

• Tendon of long head of biceps brachii (intracapsular)

• Deltoid

Anteriorly

• Subscapularis

• Coracobrachialis

• Short head of biceps 

• Deltoid

Posteriorly

• Infraspinatus

• Teres minor 

• Deltoid

Inferiorly

• Long head of triceps

•Axillary nerve

• Posterior circumflex humeral vessels

NERVE SUPPLY

The nerves supplying the joint are

• Suprascapular nerve

•Axillary nerve

• Musculocutaneous nerve

MOVEMENTS

The movements and muscles producing them, with their nerve supply.

APPLIED ANATOMY

Dislocation of Shoulder Joint

The shoulder joint is the most commonly dislocated joint in the body due to 

(i) disproportionate size of articular surfaces – head of humerus and glenoid cavity of the scapula (the head of humerus is much larger to fit properly into smaller glenoid cavity of scapula [4:1 ratio]) 

(ii) laxity of joint capsule. • Dislocation most commonly occurs inferiorly because the joint is least supported below.

Frozen Shoulder (Adhesive Capsulitis)

It is a clinical condition characterized by painful and uniform restriction of all movements of shoulder joint. It occurs due to shrinkage of joint capsule leading to adhesion between rotator cuff and head of humerus.