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Glenohumeral joint

Overview

The glenohumeral joint, commonly known as the shoulder
Shoulder
In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula. The shoulder refers to the group of structures in the region of the joint....

joint, is a multiaxial synovial

Synovial joint

A Synovial joint is the most common and most movable type of joint in the body of a mammal. As with most other joints, synovial joints achieve movement at the point of contact of the articulating bones....

ball and socket joint

Ball and socket joint

A ball and socket joint is a joint in which the distal bone is capable of motion around an indefinite number of axes, which have one common center...

and involves articulation between the glenoid fossa

Glenoid cavity

On the lateral angle of the scapula is a shallow pyriform, articular surface, the glenoid cavity , which is directed lateralward and forward and articulates with the head of the humerus; it is broader below than above and its vertical diameter is the longest.The cavity surface is covered with...

of the scapula

Scapula

In anatomy, the scapula, omo , or shoulder blade, is the bone that connects the humerus with the clavicle ....

(shoulder blade) and the head of the humerus (upper arm bone).

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.

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Encyclopedia

Synovial joint

ball and socket joint

Ball and socket joint

A ball and socket joint is a joint in which the distal bone is capable of motion around an indefinite number of axes, which have one common center...

and involves articulation between the glenoid fossa

Glenoid cavity

of the scapula

Scapula

In anatomy, the scapula, omo , or shoulder blade, is the bone that connects the humerus with the clavicle ....

(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 Scapulohumeral rhythm is the movement of the scapula across the thoracic cage in relation to the humerus. This movement can be compromised by anything that changes then position of the scapula. This could be an imbalance in the muscles that hold the scapula in place which are the upper and lower trapezium. This imbalance could cause a forward head carriage which in turn can affect the range of movements of the shoulder.

The rotator cuff

Rotator cuff

In anatomy, the rotator cuff is the group of muscles and their tendons that act to stabilize the shoulder. The four muscles of the rotator cuff, along with the teres major and the deltoid, make up the six scapulohumeral muscles of the human body.-Function:The rotator cuff muscles are...

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 Flexion In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...	Anterior fibers of deltoid Deltoid muscle In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the central...	Clavicle Clavicle In human anatomy, the clavicle or collar bone is classified as a long bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is abducted. This movement is palpable...	Middle of lateral surface of shaft of humerus Body of humerus The body or shaft of the humerus is almost cylindrical in the upper half of its extent, prismatic and flattened below, and has three borders and three surfaces.- Anterior :...
	Clavicular part of pectoralis major Pectoralis major muscle The pectoralis major is a thick, fan-shaped muscle, situated at the chest of the body. It makes up the bulk of the chest muscles in the male and lies under the breast in the female...	Clavicle	Lateral lip of bicipital groove of humerus
	Long head of biceps brachii	Supraglenoid tubercle Supraglenoid tubercle The supraglenoid tubercle is a region of the scapula to which the long head of the biceps brachii muscle attaches.-External links:... of scapula Scapula In anatomy, the scapula, omo , or shoulder blade, is the bone that connects the humerus with the clavicle ....	Tuberosity of radius Radial tuberosity Beneath the neck of the radius, on the medial side, is an eminence, the radial tuberosity; its surface is divided into:* a posterior, rough portion, for the insertion of the tendon of the biceps brachii.... , Deep fascia of forearm Antebrachial fascia The antebrachial fascia continuous above with the brachial fascia, is a dense, membranous investment, which forms a general sheath for the muscles in this region; it is attached, behind, to the olecranon and dorsal border of the ulna, and gives off from its deep surface numerous intermuscular...
	Short head of biceps brachii	Coracoid process of scapula Scapula In anatomy, the scapula, omo , or shoulder blade, is the bone that connects the humerus with the clavicle ....
	Coracobrachialis Coracobrachialis muscle The Coracobrachialis is the smallest of the three muscles that attach to the coracoid process of the scapula. It is situated at the upper and medial part of the arm....	Coracoid process	Medial aspect of shaft of humerus
Extension Extension (kinesiology) Extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of the arm would...	Posterior fibers of deltoid	Spine of scapula Spine of scapula The spine of the scapula is a prominent plate of bone, which crosses obliquely the medial four-fifths of the scapula at its upper part, and separates the supra- from the infraspinatous fossa....	Middle of lateral surface of shaft of humerus
	Latissimus dorsi Latissimus dorsi muscle The latissimus dorsi is the larger, flat, dorso-lateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region.-Actions:...	Iliac crest Iliac crest The crest of the ilium is the superior border of the wing of ilium and the superolateral margin of the greater pelvis.-Anatomy:... , lumbar fascia Lumbar fascia -Function:In addition to the usual function of fasciae, the lumbar fascia is an attachment for the gluteus maximus muscle.... , spines of lower six thoracic vertebrae Thoracic vertebrae The 12 thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper vertebrae being... , lower 3-4 rib Rib In vertebrate anatomy, ribs are the long curved bones which form the ribcage. In most vertebrates, ribs surround the chest they enable lungs to expand by expanding the chest, they also protect the lungs, heart, and other internal organs of the thorax... s, inferior angle of scapula Inferior angle of the scapula The inferior angle of the scapula, thick and rough, is formed by the union of the vertebral and axillary borders; its dorsal surface affords attachment to the Teres major and frequently to a few fibers of the Latissimus dorsi.-External links:...	Floor of bicipital groove of humerus
	Teres major Teres major muscle Teres major is a muscle of the upper limb and one of six scapulohumeral muscles. It is a thick but somewhat flattened muscle.-Origin and insertion:...	Lateral border of scapula Lateral border of the scapula The lateral border is the thickest of the three borders of the scapula.It begins above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle....	Medial lip of bicipital groove of humerus
Abduction Abduction (kinesiology) Abduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:The coming together of two bones attached by a joint laterally* of arm at shoulder...	Middle fibers of deltoid	Acromion process of scapula	Middle of lateral surface of shaft of humerus
	Supraspinatus Supraspinatus muscle The supraspinatus is a relatively small muscle of the upper limb that takes its name from its origin from the supraspinous fossa superior to the spine of the scapula. It is one of the four rotator cuff muscles and also abducts the arm at the shoulder...	Supraspinous fossa of scapula	Greater tuberosity Greater tubercle The greater tubercle of the humerus is situated lateral to the head of the humerus and posteriolateral to the lesser tubercle.Its upper surface is rounded and marked by three flat impressions.... of humerus
Adduction Adduction Adduction is a movement which brings a limb — arm or leg — closer to the sagittal plane of the body. It is opposed to abduction.This term is also used in reference to the operation of the muscle in anatomy or musculature.-Upper limb:* of arm at shoulder...	Sternal Sternum The sternum is a long flat bone shaped like a capital 'T' located in the center of the thorax... part of pectoralis major	Sternum Sternum The sternum is a long flat bone shaped like a capital 'T' located in the center of the thorax... , 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 Teres major muscle Teres major is a muscle of the upper limb and one of six scapulohumeral muscles. It is a thick but somewhat flattened muscle.-Origin and insertion:...	Lower third of lateral border of scapula Lateral border of the scapula The lateral border is the thickest of the three borders of the scapula.It begins above at the lower margin of the glenoid cavity, and inclines obliquely downward and backward to the inferior angle....	Medial lip of bicipital groove of humerus
	Teres minor Teres minor muscle -Origin and insertion:It arises from the dorsal surface of the axillary border of the scapula for the upper two-thirds of its extent, and from two aponeurotic laminæ, one of which separates it from the Infraspinatus, the other from the Teres major....	Upper two thirds of lateral border of scapula	Greater tuberosity of humerus
Lateral rotation External rotation External rotation is rotation away from the center of the body.The muscles of external rotation include:* of arm/humerus at shoulder Deltoid muscle Infraspinatus** Teres minor* of thigh/femur at hip ** Gluteus maximus...	Infraspinatus Infraspinatus muscle The Infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa. The infraspinatus is a muscle of the rotator cuff.-Origin and insertion:...	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 Internal rotation In anatomy, internal rotation is rotation towards the center of the body.The muscles of internal rotation include:* of arm/humerus at shoulder Deltoid muscle Subscapularis Teres major Latissimus dorsi...	Subscapularis Subscapularis muscle The Subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint.- Origin and insertion :...	Subscapular fossa Subscapular fossa The costal or ventral surface of the scapula presents a broad concavity, the subscapular fossa.It provides an attachment for the subscapularis muscle.-External links: - "Scapular Region: Scapula "...	Lesser tuberosity Lesser tubercle The lesser tubercle of the humerus, although smaller, is more prominent than the greater tubercle: it is situated in front, and is directed medially and anteriorly.... 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

Joint capsule

An articular capsule is an envelope surrounding a synovial joint.-Layers:Each capsule consists of two layers:* an outer layer composed of avascular white fibrous tissue...

that is lax inferiorly and therefore is at risk of dislocation

Dislocation (medicine)

Joint dislocation, or luxation , occurs when bones in a joint become displaced or misaligned. It is often caused by a sudden impact to the joint. The ligaments always become damaged as a result of a dislocation...

inferiorly. The long head of the biceps brachii muscle

Biceps brachii muscle

In human anatomy, the biceps brachii is a muscle located on the upper arm. The biceps has several functions, the most important being to rotate the forearm and to flex the elbow.-Terminology:...

travels inside the capsule to attach to the supraglenoid tubercle

Supraglenoid tubercle

The supraglenoid tubercle is a region of the scapula to which the long head of the biceps brachii muscle attaches.-External links:...

of the scapula.

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

A number of bursae

Bursa (anatomy)

A bursa is a small fluid-filled sac lined by synovial membrane with an inner capillary layer of slimy fluid . It provides a cushion between bones and tendons and/or muscles around a joint. This helps to reduce any friction between the bones and allows free movement...

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

Scapula

In anatomy, the scapula, omo , or shoulder blade, is the bone that connects the humerus with the clavicle ....

), 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

Subscapularis muscle

The Subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint.- Origin and insertion :...

, 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

Superior, middle and inferior glenohumeral ligaments
Glenohumeral ligaments
In addition to the coracohumeral ligament, three supplemental bands, which are named the glenohumeral ligaments , strengthen the capsule....
Coracohumeral ligament
Coracohumeral ligament
The coracohumeral ligament is a broad ligament which strengthens the upper part of the capsule of the shoulder joint.It arises from the lateral border of the coracoid process, and passes obliquely downward and lateralward to the front of the greater tubercle of the humerus, blending with the tendon...
Transverse humeral ligament
Transverse humeral ligament
The transverse humeral ligament is a broad band passing from the lesser to the greater tubercle of the humerus, and always limited to that portion of the bone which lies above the epiphysial line....

Pathology

The capsule can become inflamed and stiff, with abnormal bands of tissue (adhesions

Adhesion (medicine)

Adhesions are fibrous bands that form between tissues and organs, often as a result of injury during surgery. They may be thought of as internal scar tissue. In the case of frozen shoulder adhesions grow between the shoulder joint surfaces, restricting motion.Adhesions form as a natural part of...

) growing between the joint surfaces, causing pain and restricting movement of the shoulder, a condition known as frozen shoulder

Frozen shoulder

Frozen shoulder, medically referred to as adhesive capsulitis, is a disorder in which the shoulder capsule, the connective tissue surrounding the glenohumeral joint of the shoulder, becomes inflamed and stiff, and grows together with abnormal bands of tissue, called adhesions, greatly restricting...

or adhesive capsulitis.