Anatomy: Joints of Shoulder

Joints of Shoulder

Acromioclavicular joint Is a synovial plane joint that allows a gliding movement when the scapula rotates and is reinforced by the coracoclavicular ligament, which consists of the conoid and trapezoid ligaments. Sternoclavicular joint Is a double synovial plane (gliding) joint and united by the fibrous capsule. Is reinforced by the anterior and posterior sternoclavicular, interclavicular, and costoclavicular ligaments. Allows elevation and depression, protraction and retraction, and circumduction of the shoulder. Shoulder (glenohumeral) joint Is a synovial ball-and-socket joint between the glenoid cavity of the scapula and the head of the humerus. Both articular surfaces are covered with hyaline cartilage. Is surrounded by the fibrous capsule that is attached superiorly to the margin of the glenoid cavity and inferiorly to the anatomic neck of the humerus. The capsule is reinforced by the rotator cuff, the glenohumeral ligaments , and the coracohumeral ligaments. Has a cavity that is deepened by the fibrocartilaginous glenoid labrum ; communicates with the subscapular bursa; and allows abduction and adduction, flexion and extension, and circumduction and rotation. Is innervated by the axillary, suprascapular, and lateral pectoral nerves. Receives blood from branches of the suprascapular, anterior and posterior humeral circumflex, and scapular circumflex arteries. May be subject to inferior or anterior dislocation , which stretches the fibrous capsule, avulses the glenoid labrum, and may injure the axillary nerve.

Rotator cuff

Is formed by the tendons of the supraspinatus, infraspinatus, teres minor, and subscapularis ; fuses with the joint capsule; and provides mobility. Keeps the head of the humerus in the glenoid fossa during movements and thus stabilizes the shoulder joint.

Ligaments of the shoulder joint

Glenohumeral ligaments Extend from the supraglenoid tubercle to the upper part of the lesser tubercle of the humerus (superior glenohumeral ligament ), to the lower anatomic neck of the humerus (middle glenohumeral ligament ), and to the lower part of the lesser tubercle of the humerus (inferior glenohumeral ligament ). Transverse humeral ligament Extends between the greater and lesser tubercles, and holds the tendon of the long head of the biceps in the intertubercular groove. Coracohumeral ligament Extends from the coracoid process to the greater tubercle. Coracoacromial ligament Extends from the coracoid process to the acromion.

Bursae around the shoulder

Form a lubricating mechanism between the rotator cuff and the coracoacromial arch during movement of the shoulder joint. Subacromial bursa Lies between the coracoacromial arch and the supraspinatus muscle, and usually communicates with the subdeltoid bursa. Protects the supraspinatus tendon against friction with the acromion. Subdeltoid bursa Lies between the deltoid muscle and the shoulder joint capsule and usuallycommunicates with the subacromial bursa. Facilitates the movement of the deltoid muscle over the joint capsule and the supraspinatus tendon. Subscapular bursa Lies between the subscapularis tendon and the neck of the scapula. Communicates with the synovial cavity of the shoulder joint.