shoulder The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder mak ...

ball-and-socket joint The ball-and-socket joint (or spheroid joint) is a type of synovial joint in which the ball-shaped surface of one rounded bone fits into the cup-like depression of another bone. The distal bone is capable of motion around an indefinite number of ...

glenoid fossa The glenoid fossa of the scapula or the glenoid cavity is a bone part of the shoulder. The word ''glenoid'' is pronounced or (both are common) and is from el, gléne, "socket", reflecting the shoulder joint's ball-and-socket form. It is a sha ...

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

joint capsule In anatomy, a joint capsule or articular capsule is an envelope surrounding a synovial joint. The shoulder joint is a ball-and-socket joint between the scapula and the humerus. The socket of the glenoid fossa of the scapula is itself quite shallow, but it is made deeper by the addition of the

glenoid labrum The glenoid labrum (glenoid ligament) is a fibrocartilaginous structure (not a fibrocartilage as previously thought) rim attached around the margin of the glenoid cavity in the shoulder blade. The shoulder joint is considered a ball and socket ...

. The glenoid labrum is a ring of cartilaginous fibre attached to the circumference of the cavity. This ring is continuous with the

tendon A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

of the

biceps brachii The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join t ...

above.

Spaces

Significant joint spaces are: * The normal glenohumeral space is 4–5 mm. Subacromial space on outlet view X-ray

* The normal subacromial space in shoulder radiographs is 9–10 mm; this space is significantly greater in men, with a slight reduction with age. In middle age, a subacromial space less than 6 mm is pathological, and may indicate a rupture of the tendon of the

supraspinatus muscle The supraspinatus (plural ''supraspinati'') is a relatively small muscle of the upper back that runs from the supraspinous fossa superior portion of the scapula (shoulder blade) to the greater tubercle of the humerus. It is one of the four rotator ...

. The

axillary space The axillary spaces are anatomic spaces. through which axillary contents leave the axilla. They consist of the quadrangular space, triangular space, and triangular interval. It is bounded by teres major, teres minor, medial border of the humerus, ...

is an

anatomic space {{set index article In anatomy, a spatium or anatomic space is a space (cavity or gap). Anatomic spaces are often landmarks to find other important structures. When they fill with gases (such as air) or liquids (such as blood) in pathological ways, ...

between the associated muscles of the shoulder. This space transmits the

subscapular artery The subscapular artery, the largest branch of the axillary artery, arises from the third part of the axillary artery at the lower border of the subscapularis muscle, which it follows to the inferior angle of the scapula, where it anastomoses wi ...

and the

axillary nerve The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. The a ...

.

Capsule

The shoulder joint has a very loose

joint capsule In anatomy, a joint capsule or articular capsule is an envelope surrounding a synovial joint.dislocate. The "U shaped" dependent portion of the axillary part of the capsule located between the anterior and posterior bands of inferior glenohumeral ligament is called "axillary pouch". Synovium extends below the long head of biceps and subscapularis tendon to form subscapular bursa. Therefore, long head of biceps is extrasynovial and intracapsular, attaching to

supraglenoid tubercle The supraglenoid tubercle is a region of the scapula from which the long head of the biceps brachii muscle originates. It is a small, rough projection superior to the glenoid cavity near the base of the coracoid process. The term supraglenoid is ...

.

Bursae

A number of small fluid-filled sacs known as

synovial bursa Synovial () may refer to: * Synovial fluid * Synovial joint * Synovial membrane * Synovial bursa Synovial () may refer to: * Synovial fluid * Synovial joint * Synovial membrane The synovial membrane (also known as the synovial stratum, synovi ...

e are located around the capsule to aid mobility: * Between the joint capsule and the

deltoid muscle The deltoid muscle is the muscle forming the rounded contour of the human shoulder. It is also known as the 'common shoulder muscle', particularly in other animals such as the domestic cat. Anatomically, the deltoid muscle appears to be made up o ...

is the subacromial-subdeltoid bursa. * Between the capsule and the

acromion In human anatomy, the acromion (from Greek: ''akros'', "highest", ''ōmos'', "shoulder", plural: acromia) is a bony process on the scapula (shoulder blade). Together with the coracoid process it extends laterally over the shoulder joint. The acro ...

is the

subacromial bursa The subacromial bursa is the synovial cavity located just below the acromion, which communicates with the subdeltoid bursa in most individuals, forming the so-called subacromial-subdeltoid bursa (SSB). The SSB bursa is located deep to the deltoid ...

. * The

subcoracoid bursa The subcoracoid bursa or subcoracoid bursa of Collas is a synovial bursa located in the shoulder. It is located anterior to the subscapularis muscle and inferior to the coracoid process. Its function is to reduce friction between the coracobrachi ...

is between the capsule and the

coracoid process The coracoid process (from Greek κόραξ, raven) is a small hook-like structure on the lateral edge of the superior anterior portion of the scapula (hence: coracoid, or "like a raven's beak"). Pointing laterally forward, it, together with the ...

of the scapula. * The coracobrachial bursa is between the

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. Structure It arises from its medial two-thirds and Som ...

and the tendon of the

coracobrachialis muscle The coracobrachialis muscle is the smallest of the three muscles that attach to the coracoid process of the scapula. (The other two muscles are pectoralis minor and the short head of the biceps brachii.) It is situated at the upper and medial part ...

. * Between the capsule and the tendon of the subscapularis muscle is the subscapular bursa, this is also known as the subtendinous bursa of the scapularis. The

supra-acromial bursa The supra-acromial bursa is located on the superior aspect of the acromion and normally does not communicate with the glenohumeral joint.Resnick D. Diagnosis of bone and joint disorders. 3rd edition. Philadelphia: WB Saunders Company; 1995. Supra-a ...

does not normally communicate with the shoulder joint.

Muscles

The shoulder joint is a muscle-dependent joint as it lacks strong ligaments. The primary stabilizers of the shoulder include the biceps brachii on the anterior side of the arm, and tendons of the

rotator cuff The rotator cuff is a group of muscles and their tendons that act to stabilize the human shoulder and allow for its extensive range of motion. Of the seven scapulohumeral muscles, four make up the rotator cuff. The four muscles are the supraspi ...

; which are fused to all sides of the capsule except the inferior margin. The tendon of the long head of the biceps brachii passes through the

bicipital groove The bicipital groove (intertubercular groove, sulcus intertubercularis) is a deep groove on the humerus that separates the greater tubercle from the lesser tubercle. It allows for the long tendon of the biceps brachii muscle to pass. Structure ...

on the humerus and inserts on the superior margin of the glenoid cavity to press the

head of the humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a round ...

against the glenoid cavity. Other long muscles such as pectoralis major, latissimus dorsi, teres major and deltoid muscles also provide support to the shoulder joint. The tendons of the rotator cuff and their respective muscles (

supraspinatus muscle The supraspinatus (plural ''supraspinati'') is a relatively small muscle of the upper back that runs from the supraspinous fossa superior portion of the scapula (shoulder blade) to the greater tubercle of the humerus. It is one of the four rotator ...

,

infraspinatus In human anatomy, the infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa.''Gray's Anatomy'', see infobox. As one of the four muscles of the rotator cuff, the main function of the infraspina ...

,

teres minor The teres minor (Latin ''teres'' meaning 'rounded') is a narrow, elongated muscle of the rotator cuff. The muscle originates from the lateral border and adjacent posterior surface of the corresponding right or left scapula and inserts at both the ...

, and

subscapularis 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. Structure It arises from its medial two-thirds and Som ...

) stabilize and fix the joint. The supraspinatus, infraspinatus and teres minor muscles aid in abduction and external rotation.

Ligaments

* Superior, middle and inferior

glenohumeral ligaments In human anatomy, the glenohumeral ligaments (GHL) are three ligaments on the anterior side of the glenohumeral joint (i.e. between the glenoid cavity of the scapula and the head of the humerus; colloquially called the shoulder joint). Reinforcin ...

. It is the thickenings of the capsule that pass from the upper part of glenoid to lesser tuberosity and inferior part of the head of humerus. These ligaments are weak unlike its posterior part which is supported by the

infraspinatus In human anatomy, the infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa.''Gray's Anatomy'', see infobox. As one of the four muscles of the rotator cuff, the main function of the infraspina ...

muscle. *

Coracohumeral ligament The coracohumeral ligament is a broad ligament of the shoulder. It attaches to the coracoid process at one end, and to the greater and lesser tubercles of the humerus at the other (as two discrete bands). It strengthens the upper part of the join ...

*

Transverse humeral ligament The transverse humeral ligament (Brodie's ligament) forms a broad band bridging the lesser and greater tubercle of the humerus. Its attachments are limited superior to the epiphysial line. By enclosing the canal of the bicipital groove The bici ...

*

Coraco-acromial ligament The coracoacromial ligament is a strong triangular ligament between the coracoid process and the acromion. It protects the head of the humerus. Its acromial attachment may be repositioned to the clavicle during reconstructive surgery of the acrom ...

Innervation

The nerves supplying the shoulder joint all arise in the

brachial plexus The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in th ...

. They are the

suprascapular nerve The suprascapular nerve is a nerve that branches from the upper trunk of the brachial plexus. It is responsible for the innervation of two of the muscles that originate from the scapula, namely the supraspinatus muscle, supraspinatus and infraspina ...

, the

axillary nerve The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. The a ...

and the

lateral pectoral nerve The lateral pectoral nerve (also known as the lateral anterior thoracic nerve) arises from the lateral cord of the brachial plexus, and through it from the C5-7. It passes across the axillary artery and vein, pierces the clavipectoral (coracocl ...

.

Blood supply

The shoulder joint is supplied with blood by branches of the

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

and posterior circumflex humeral arteries, the

suprascapular artery The suprascapular artery is a branch of the thyrocervical trunk on the neck. Structure At first, it passes downward and laterally across the scalenus anterior and phrenic nerve, being covered by the sternocleidomastoid muscle; it then crosses t ...

and the

scapular circumflex artery The circumflex scapular artery (scapular circumflex artery, dorsalis scapulae artery) is a branch of the subscapular artery and part of the scapular anastomoses. It curves around the axillary border of the scapula, traveling through the anatom ...

.

Function

Shoulder motion with rotator cuff (supraspinatus)

The

rotator cuff The rotator cuff is a group of muscles and their tendons that act to stabilize the human shoulder and allow for its extensive range of motion. Of the seven scapulohumeral muscles, four make up the rotator cuff. The four muscles are the supraspi ...

muscles of the shoulder produce a high

tensile In physics, tension is described as the pulling force transmitted axially by the means of a string, a rope, chain, or similar object, or by each end of a rod, truss member, or similar three-dimensional object; tension might also be described as t ...

force, and help to pull the head of the humerus into the glenoid cavity. The glenoid cavity is shallow and contains the

glenoid labrum The glenoid labrum (glenoid ligament) is a fibrocartilaginous structure (not a fibrocartilage as previously thought) rim attached around the margin of the glenoid cavity in the shoulder blade. The shoulder joint is considered a ball and socket ...

which deepens it and aids stability. With 120 degrees of unassisted flexion, the shoulder joint is the most mobile joint in the body. Shoulder muscle - force couple of rotator cuff

Shoulder muscle - force couple of rotator cuff

The movement of the scapula across the

rib cage The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi- ...

in relation to the humerus is known as the ''scapulohumeral rhythm'', and this helps to achieve a further range of movement. This range can be compromised by anything that changes the position of the scapula. This could be an imbalance in parts of the large

trapezius muscle The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports the ...

s that hold the scapula in place. Such an imbalance could cause a forward head carriage which in turn can affect the range of movements of the shoulder.

Movements

* Flexion and extension of the shoulder joint in the (

sagittal plane The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divid ...

). **Flexion is carried out by the anterior fibres of the deltoid,

pectoralis major The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, a ...

and the coracobrachialis. **Extension is carried out by the

latissimus dorsi The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from L ...

and posterior fibres of the deltoid. * Abduction and adduction of the shoulder (

frontal plane The coronal plane (also known as the frontal plane) is an anatomical plane that divides the body into dorsal and ventral sections. It is perpendicular to the sagittal and transverse planes. Details The coronal plane is an example of a longitud ...

). **Abduction is carried out by the deltoid and the supraspinatus in the first 90 degrees. From 90-180 degrees it is the trapezius and the

serratus anterior The serratus anterior is a muscle that originates on the surface of the 1st to 8th ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula. The serratus anterior acts to pull the scapula fo ...

. ** Adduction is carried out by the pectoralis major, latissimus dorsi, teres major and the subscapularis. * Horizontal abduction and horizontal adduction of the shoulder (transverse plane) * Medial and lateral rotation of the shoulder (also known as internal and external rotation). **Medial rotation is carried out by the anterior fibres of the deltoid, teres major, subscapularis, pectoralis major and the latissimus dorsi. **Lateral rotation is carried out by the posterior fibres of the deltoid, infraspinatus and the teres minor. * Circumduction of the shoulder (a combination of flexion/extension and abduction/adduction).

Clinical significance

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

adhesions 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 that connects tissues not normally connected. Pathophysiology Adhesions form as a natural ...

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

frozen shoulder Adhesive capsulitis, also known as frozen shoulder, is a condition associated with shoulder pain and stiffness. It is a common shoulder ailment that is marked by pain and a loss of range of motion, particularly in external rotation. There is a ...

or adhesive capsulitis. A

SLAP tear Slap or slapping may refer to: * Slapping (strike), a method of striking with the palm of the hand * Slapping (music), a musical technique used with stringed instruments * Slap tonguing, a musical technique used on wind instruments * ''Slap'' (m ...

(superior labrum anterior to posterior) is a rupture in the glenoid labrum. SLAP tears are characterized by shoulder pain in specific positions, pain associated with overhead activities such as tennis or overhand throwing sports, and weakness of the shoulder. This type of injury often requires surgical repair. Anterior dislocation of the glenohumeral joint occurs when the humeral head is displaced in the anterior direction. Anterior shoulder dislocation often is a result of a blow to the shoulder while the arm is in an abducted position. In younger people, these dislocation events are most commonly associated with fractures on the humerus and/or glenoid and can lead to recurrent instability. In older people, recurrent instability is rare but people often suffer rotator cuff tears. It is not uncommon for the arteries and nerves (

axillary nerve The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. The a ...

) in the axillary region to be damaged as a result of a shoulder dislocation; which if left untreated can result in weakness, muscle atrophy, or paralysis.

Subacromial bursitis Subacromial bursitis is a condition caused by inflammation of the Synovial bursa, bursa that separates the superior surface of the supraspinatus muscle, supraspinatus tendon (one of the four tendons of the rotator cuff) from the overlying coraco-ac ...

is a painful condition caused by

inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...

which often presents a set of symptoms known as subacromial impingement.

Arthrography An arthrogram is a series of images of a joint after injection of a contrast medium, usually done by fluoroscopy or MRI. The injection is normally done under a local anesthetic such as Novocain or lidocaine. The radiologist or radiographer perfor ...

of shoulder joint (with or without computed tomography) is performed by injecting contrast below and lateral to the

coracoid process The coracoid process (from Greek κόραξ, raven) is a small hook-like structure on the lateral edge of the superior anterior portion of the scapula (hence: coracoid, or "like a raven's beak"). Pointing laterally forward, it, together with the ...

to outline the shoulder joint. Axillary pouch of the shoulder can be seen on external rotation, while subscapular (subcoracoid) bursa can be seen on internal rotation of arm. The contrast should not enter

subacromial bursa The subacromial bursa is the synovial cavity located just below the acromion, which communicates with the subdeltoid bursa in most individuals, forming the so-called subacromial-subdeltoid bursa (SSB). The SSB bursa is located deep to the deltoid ...

unless supraspinatus tendon is completely ruptured. MRI with surface coils is used to image the shoulder joint.

Additional images

File:Shoulder joint.svg, Diagram of the human shoulder joint, front view File:Shoulder joint back-en.svg, Diagram of the human shoulder joint, back view File:Gray326.png, The left shoulder and

acromioclavicular joint The acromioclavicular joint, or AC joint, is a joint at the top of the shoulder. It is the junction between the acromion (part of the scapula that forms the highest point of the shoulder) and the clavicle. It is a plane synovial joint. Structure ...

s, and the proper ligaments of the scapula File:Slide1KKKK.JPG, Dissection image of the coracohumeral ligament of the glenohumeral joint in green File:Slide7KKKK.JPG, Dissection image of the cartilage of the glenohumeral joint in green

References

External links

Overview at brown.edu

*
Diagram at yess.uk.com
{{DEFAULTSORT:Glenohumeral Joint Joints Upper limb anatomy

Spaces

Capsule

Bursae

Muscles

Ligaments

Innervation

Blood supply

Function

Movements

Clinical significance

Additional images

See also

References

External links