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A Brief Description: Shoulder Joint Anatomy

The shoulder is one of the largest and most complex joints in the body. The shoulder joint is formed where the humerus (upper arm bone) fits into the scapula (shoulder blade), like a ball and socket.

Shoulder include:

The different layers of the shoulder are built and connected can help understand how the shoulder works and is affected by injury and overuse.

Gross Anatomy

Osteology

Scapula

The scapula is a triangular-shaped bone that functions mainly as a site for muscle attachment. Four rotator cuff muscles that act on the shoulder take their origin from the scapula. These are the supraspinatus, infraspinatus, teres minor, and subscapularis.

The scapula hasThe glenoid cavity (or, alternatively, the glenoid fossa) is set on the expanded aspect of the lateral angle of the scapula.

Clavicle

The clavicle is an S-shaped bone that forms the anterior portion of the shoulder girdle that keeps the arm away from the trunk, allowing it to move freely. The clavicle has 2 articulations, the sternoclavicular joint and the acromioclavicular joint.

Humeral head

The proximal articular surface of the humerus is termed the humeral head. The humeral head articulates against the shallow glenoid cavity.

Articulations

Sternoclavicular joint

The sternoclavicular joint is the sole connection between the axial skeleton and the upper extremity. The sternoclavicular joint allows upward elevation, anteroposterior movement, and rotation about the long axis of the clavicle.

Acromioclavicular joint

The acromioclavicular (AC) joint is the only articulation between the clavicle and scapula. The AC joint is an encapsulated diarthrodial joint held together by its joint capsule and the coracoacromial ligaments: the trapezoid and conoid ligaments.

Glenohumeral joint

The glenohumeral joint is the main articulation of the shoulder joint. It is the multi-axial ball-and-socket synovial joint formed by the articular surfaces of the glenoid cavity and the head of the humerus.

Labrum

The glenoid labrum is a ring composed of mostly dense fibrous tissue. The average depth of the glenoid cavity is 2.5 mm, but the labrum serves to increase this depth.

Ligaments

Coracoclavicular

The conoid and trapezoid ligaments comprise the coracoclavicular ligaments (CCLs). They function to maintain the articulation of the clavicle with the coracoid process of the scapula.

Glenohumeral

Three glenohumeral ligaments exist: (1) the superior glenohumeral ligament (SGHL), (2) the middle glenohumeral ligament (MGHL), and (3) the inferior glenohumeral ligament (IGHL).

Coracohumeral

The coracohumeral ligament (CHL) originates on the base and lateral border of the coracoid process of the scapula and inserts on the greater tubercle.

Rotator cuff

The supraspinatus, infraspinatus, teres minor, and subscapularis muscles comprise the rotator cuff. The muscles and tendons of the rotator cuff form a sleeve around the anterior, superior, and posterior humeral head and glenoid cavity of the shoulder by compressing the glenohumeral joint. In addition to stabilization, the rotator cuff provides the shoulder with tremendous mobility.

Subacromial/subdeltoid Bursa

The subacromial bursa lies on the superior aspect of the supraspinatus tendon. The bursa acts to cushion and reduce friction during motion between the overlying bone of the acromion and the soft rotator cuff muscles below. It often extends laterally to be continuous with the subdeltoid bursa.

Shoulder Conditions

 

 

 

 

 

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