Question 2. Describe the Shoulder Joint (Glenohumeral Joint) under the following headings: (a) classification, (b) articular surfaces, (c) ligaments, (d) relations, (e) nerve supply, (f) movements and (g) applied anatomy.
Answer.
Shoulder Joint (Glenohumeral Joint) Classification
Synovial joint of ball and socket type.
Shoulder Joint (Glenohumeral Joint) Articular surfaces
They are formed by the large hemispherical head of humerus and shallow glenoid cavity of scapula.
Read And Learn More: Selective Anatomy Notes And Question And Answers
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.
Shoulder Joint 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:
- 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, extending 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.
Shoulder Joint (Glenohumeral Joint) Relations
Shoulder Joint Superiorly
- Coracoacromial arch
- Subacromial bursa
- Supraspinatus
- Tendon of long head of biceps brachii (intracapsular)
- Deltoid
Shoulder Joint Anteriorly
- Subscapularis
- Coracobrachialis
- Short head of biceps
- Deltoid
Shoulder Joint Posteriorly
- Infraspinatus
- Teres minor
- Deltoid
Shoulder Joint Inferiorly
- Long head of triceps
- Axillary nerve
- Posterior circumflex humeral vessels
Shoulder Joint Nerve supply
The nerves supplying the joint are
- Suprascapular nerve
- Axillary nerve
- Musculocutaneous nerve
Shoulder Joint Movements
The movements and muscles producing them, with their nerve supply.
Movements of Shoulder Joint and Muscles Producing Them with Their Nerve Supply
Shoulder Joint (Glenohumeral Joint) 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]) and (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.
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