Glenohumeral joint

Glenohumeral joint

The glenohumeral joint, commonly known as the shoulder joint, is a synovial ball and socket joint and involves articulation between the glenoid fossa of the scapula (shoulder blade) and the head of the humerus (upper arm bone).

Movements

The glenoid fossa is shallow and contains the glenoid labrum which deepens it and aids in stability. With 120 degrees of unassisted flexion, the glenohumeral joint is the most mobile joint in the body.

Scapulohumeral rhythm helps to achieve further range of movement.

The rotator cuff muscles of the shoulder produce a high tensile force, and help to pull the head of the humerus into the glenoid fossa.

Movements of the shoulder joint
Movement Muscles Origin Insertion
Flexion Anterior fibers of deltoid Clavicle Middle of lateral surface of shaft of humerus
Clavicular part of pectoralis major Clavicle Lateral lip of bicipital groove of humerus
Long head of biceps brachii Supraglenoid tubercle of scapula Tuberosity of radius, Deep fascia of forearm
Short head of biceps brachii Coracoid process of scapula
Coracobrachialis Coracoid process Medial aspect of shaft of humerus
Extension Posterior fibers of deltoid Spine of scapula Middle of lateral surface of shaft of humerus
Latissimus dorsi Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3-4 ribs, inferior angle of scapula Floor of bicipital groove of humerus
Teres major Lateral border of scapula Medial lip of bicipital groove of humerus
Abduction Middle fibers of deltoid Acromion process of scapula Middle of lateral surface of shaft of humerus
Supraspinatus Supraspinous fossa of scapula Greater tuberosity of humerus
Adduction Sternal part of pectoralis major Sternum, upper six costal cartilages Lateral lip of bicipital groove of humerus
Latissimus dorsi Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3-4 ribs, inferior angle of scapula Floor of bicipital groove of humerus
Teres major Lower third of lateral border of scapula Medial lip of bicipital groove of humerus
Teres minor Upper two thirds of lateral border of scapula Greater tuberosity of humeruis
Lateral rotation Infraspinatus Infraspinous fossa of scapula Greater tuberosity of humerus
Teres minor Upper two thirds of lateral border of scapula Greater tuberosity of humerus
Posterior fibers of deltoid Spine of scapula Middle of lateral surface of shaft of humerus
Medial rotation Subscapularis Subscapular fossa Lesser tuberosity of humerus
Latissimus dorsi Iliac crest, lumbar fascia, spines of lower 3-4 ribs, inferior angle of scapula Floor of bicipital groove of humerus
Teres major Lower third of lateral border of scapula Medial lip of bicipital groove of humerus
Anterior fibers of deltoid Clavicle Middle of lateral surface of shaft of humerus

Capsule

The glenohumeral joint has a loose capsule that is lax inferiorly and therefore is at risk of dislocation inferiorly. The long head of the biceps brachii muscle travels inside the capsule to attach to the supraglenoid tubercle of the scapula.

Because the tendon is inside the capsule, it requires a synovial tendon sheath to minimize friction.

A number of bursae in the capsule aid mobility. Namely, they are the subdeltoid bursa (between the joint capsule and deltoid muscle), subcoracoid bursa (between joint capsule and coracoid process of scapula), coracobrachial bursa (between subscapularis muscle and tendon of coracobrachialis muscle), subacromial bursa (between joint capsule and acromion of scapula) and the subscapular bursa (between joint capsule and tendon of subscapularis muscle, also known as subtendinous bursa of subscapularis muscle). The bursa are formed by the synovial membrane of the joint capsule. An inferior pouching of the joint capsule between teres minor and subscapularis is known as the axillary recess.

It is important to note that the shoulder joint is a muscle dependent joint as it lacks strong ligaments.

Ligaments

Pathology

The capsule can become inflamed and stiff, with abnormal bands of tissue (adhesions) growing between the joint surfaces, causing pain and restricting movement of the shoulder, a condition known as frozen shoulder or adhesive capsulitis.

Additional images

Notes

References

  • Snell, Richard S. Clinical Anatomy by Systems. Lippincott Williams & Wilkins. (CD-ROM/PDF)

External links

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