Shoulder

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Shoulder

In human anatomy

Human anatomy

Human anatomy, which, with physiology and biochemistry, is a complementary basic medical science is primarily the scientific study of the morphology of the adult human body....
, the shoulder joint comprises the part of the body where the humerus

Humerus

Scapula

In anatomy, the scapula, omo, or shoulder blade, is the bone that connects the humerus with the clavicle .The scapula forms the posterior part of the shoulder girdle....
. The shoulder refers to the group of structures in the region of the joint.

It is made up of three bones: the clavicle

Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat 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 Abduction ....
(collarbone), the scapula

Scapula

Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.Anatomically, it connects the scapula and the ulna, and consists of the following three sections:...
(upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joint

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally....
s.

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In human anatomy

Human anatomy

Humerus

Scapula

Clavicle

Scapula

Humerus

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally....
s. The shoulder must be flexible for the wide range of motion required in the arms and hands and also strong enough to allow for actions such as lifting, pushing and pulling. The compromise between these two functions results in a large number of shoulder problems

Shoulder problems

Shoulder problems, including pain, are one of the more common reasons for physician visits for musculoskeletal symptoms. The shoulder is the most movable joint in the body....
not faced by other joints such as the hip

Hip (anatomy)

In anatomy, the hip or coxa in medical termonology is the bone projection of the femur which is known as the greater trochanter, and the overlying muscle and fat....
.

Joints of the shoulder

There are three joint

Joint

Glenohumeral joint

The glenohumeral joint

Glenohumeral joint

The glenohumeral joint, commonly known as the shoulder joint, is a multiaxial synovial joint ball and socket joint and involves articulation between the glenoid cavity of the scapula and the head of the humerus ....
is the main joint of the shoulder and the generic term "shoulder joint" usually refers to it. It is a 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....
that allows the arm to rotate in a circular fashion or to hinge out and up away from the body. It is formed by the articulation between the head of the humerus and the lateral scapula. The "ball" of the joint is the rounded, medial anterior surface of the humerus and the "socket" is formed by 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 dish-shaped portion of the lateral scapula. The shallowness of the fossa and relatively loose connections between the shoulder and the rest of the body allows the arm to have tremendous mobility, at the expense of being much easier to dislocate than most other joints in the body.

The capsule

Joint capsule

An articular capsule is an envelope surrounding a synovial joint....
is a soft tissue envelope that encircles the glenohumeral joint and attaches to the scapula

Scapula

In anatomy, the scapula, omo, or shoulder blade, is the bone that connects the humerus with the clavicle .The scapula forms the posterior part of the shoulder girdle....
, humerus

Humerus

Biceps

Biceps may refer to:* The two-headed Biceps brachii muscle on the inside of each upper arm.* The biceps femoris, one of the hamstring muscles of the underside of each thigh....
. It is lined by a thin, smooth synovial membrane. This capsule is strengthened by the coracohumeral ligament which attaches the coracoid process of the scapula to the greater tubercle of the humerus. There are also three other ligaments attaching the lesser tubercle of the humerus to lateral scapula and are collectively called the glenohumeral ligaments.

There is also a ligament

Ligament

Ligaments connect bone to bone. In anatomy, the term ligament is used to denote three different types of structures:# Fibrous Tissue that connects bones to other bones....
called semicirculare humeri which is a transversal band between the posterior sides of the tuberculum minus and majus of the humerus. This band is one of the most important strengthening ligaments of the joint capsule

Joint capsule

An articular capsule is an envelope surrounding a synovial joint....
.

Acromioclavicular joint

The acromioclavicular

Acromioclavicular joint

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

The capsule of this joint is reinforced by the coracoclavicular ligament between the scapula and clavicle at the point of articulation. The coracoclavicular ligament in further detail is created by the conoid ligament, medial from the coracoid process of the scapula and inserts on the conoid tubercle of the clavicle. Lateral to the conoid ligament is the trapezoid ligament, which runs from the coracoid process of the scapula to the trapezoid line of the clavicle. One more ligament, the coracoacromial ligament, running from the coracoid process to the acromion of the scapula contributes to the integrity of the acromioclavicular joint.

Sternoclavicular joint

The sternoclavicular occurs at the medial end of the clavicle with the manubrium

Manubrium

The manubrium or manubrium sterni is the broad, upper part of the sternum. With a quadrangular shape, wider superiorly and narrower inferiorly, it articulates with the clavicles and the first two ribs....
or top most portion of the sternum. The clavicle is triangular and rounded and the manubrium is convex the two bones articulate. The joint consists of a tight capsule and complete intra-articular disc which ensures stability of the joint. The costoclavicular ligament is the main limitation to movement, therefore, the main stabiliser of the joint. A fibrocartilaginous disc present at the joint increases the range of movement. Sternoclavicular subluxation is rare, however can be caused by direct trauma.

Movements of the shoulder

The muscles and joints of the shoulder allow it to move through a remarkable range of motion

Range of motion

Range of motion or , as used in the biomedical and weightlifting communities, is the measurement of the achievable distance between the flexed position and the extended position of a particular joint or muscle group....
, making it the most mobile joint in the human body. The shoulder can abduct

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....
, adduct

Adduction

Adduction is a movement which brings a limb ? arm or leg ? closer to the Sagittal#Planes 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....
(such as during the shoulder fly

Fly (exercise)

A fly is a strength training exercise in which the hand and arm move through an range of motion while the elbow is kept at a constant angle. Flies are used to work the muscles of the Torso....
), rotate, be raised in front of and behind the torso

Torso

Torso is an anatomical term for the central part of the many animal bodies from which extend the neck and limbs. It is sometimes referred to as the trunk....
and move through a full 360° in the sagittal plane

Sagittal plane

A sagittal plane of the human body is an imaginary plane that travels from the top to the bottom of the body, dividing it into left and right portions....
. This tremendous range of motion also makes the shoulder extremely unstable, far more prone to 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....
and injury than other joints.

Major muscles

The muscles that are responsible for movement in the shoulder attach to the scapula, humerus, and clavicle. The muscles that surround the shoulder form the shoulder cap and underarm

Underarm

The axilla is the area on the human body directly under the joint where the arm connects to the shoulder....
.

Name	Attachment	Function >- \| serratus anterior	Originates on the surface of the upper eight ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula.	- \| subclavius	Located inferior to the clavicle, originating on the first rib First rib The first rib is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward.... and inserting (penetrating) on the subclavian groove Subclavian groove On the medial part of the clavicle is a broad rough surface, the costal tuberosity , rather more than 2 cm. in length, for the attachment of the costoclavicular ligament.... of the clavicle.	- \| pectoralis minor	Arises from the third, fourth, and fifth ribs, near their cartilage and inserts into the medial border and upper surface of the coracoid process of the scapula.	- \| sternocleidomastoid	Attaches to the sternum Sternum The sternum is a long flat bone located in the center of the chest . It connects to the rib via cartilage, forming the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma.... (sterno-), the clavicle Clavicle In human anatomy, the clavicle or collar bone is classified as a flat 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 Abduction .... (cleido-), and the mastoid process Mastoid process The mastoid process is a conical prominence projecting from the undersurface of the mastoid portion of the temporal bone. It is located just behind the external acoustic meatus, and lateral to the styloid process .... of the temporal bone Temporal bone The temporal bones are situated at the sides and base of the skull.The temporal bone supports that part of the face known as the temple .... of the skull.	- \| levator scapulae	Arises from the transverse processes of the first four cervical vertebrae Cervical vertebrae In vertebrates, cervical vertebrae are those vertebrae immediately behind the skull.... and inserts into the vertebral border of the scapula.	- \| rhomboid major and rhomboid minor (work together)	They arise from the spinous processes of the 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 much smaller than those in the lower part of the... T1 to T5 as well as from the spinous processes of the seventh cervical and first thoracic vertebrae. They insert on the medial border of the scapula, from about the level of the scapular spine to the scapula's inferior angle.	- \| trapezius	Arises from the occipital bone Occipital bone The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the skull, is trapezoid in shape and curved on itself. It is pierced by a large oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal.... , the ligamentum nuchae, the spinous process of the seventh cervical, and the spinous processes of all the thoracic vertebrae, and from the corresponding portion of the supraspinal ligament. It inserts on the lateral clavicle, the acromion process Acromion process The acromion process, or simply the acromion , is an anatomy feature on the shoulder blade , together with the coracoid process extending laterally over the Glenohumeral joint.... , and into the spine of the scapula.	Different portions of the fibers perform different actions on the scapula: depression, upward rotation, elevation, and adductions.
deltoid Deltoid muscle In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder.It was previously called the Deltoideus and the name is still used by some anatomists.... , anterior fibers	Arises from the anterior border and upper surface of the lateral third of the clavicle Clavicle In human anatomy, the clavicle or collar bone is classified as a flat 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 Abduction .... .	The anterior fibres are involved in shoulder abduction when the shoulder is externally rotated. The anterior deltoid is weak in strict transverse flexion but assists the pectoralis major during shoulder transverse flexion / shoulder flexion (elbow slightly inferior to shoulders).
deltoid Deltoid muscle In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder.It was previously called the Deltoideus and the name is still used by some anatomists.... , middle fibers	Arises from the lateral margin and upper surface of the acromion.	The middle fibres are involved in shoulder abduction when the shoulder is internally rotated, are involved in shoulder flexion when the shoulder is internally rotated, and are involved in shoulder transverse abduction (shoulder externally rotated) -- but are not utilized significantly during strict transverse extension (shoulder internally rotated).
deltoid Deltoid muscle In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder.It was previously called the Deltoideus and the name is still used by some anatomists.... , posterior fibers	Arises from the lower lip of the posterior border of the spine of the scapula, as far back as the triangular surface at its medial end.	The posterior fibres are strongly involved in transverse extension particularly since the latissimus dorsi muscle 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.... is very weak in strict transverse extension. The posterior deltoid is also the primary shoulder hyperextensor.

Rotator cuff

The rotator cuff

Rotator cuff

The rotator cuff is an human anatomy term given to the group of muscles and their tendons that act to stabilize the shoulder. Along with the teres major muscle and the deltoid muscle, the four muscles of the rotator cuff make up the six scapulohumeral muscles of the human body....
is an anatomical term given to the group of muscles and their tendons that act to stabilize the shoulder. It is composed of the tendons and muscles (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....
, infraspinatus

Infraspinatus muscle

The Infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa....
, teres minor

Teres minor muscle

The Teres minor is a narrow, elongated muscle of the rotator cuff....
and 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....
) that hold the head of the humerus (ball) in the glenoid fossa (socket).

Two filmy sac-like structures called bursa

Bursa (anatomy)

A bursa is a small fluid-filled sac made of white fibrous tissue and lined with synovial membrane. It provides a cushion between bones and tendons and/or muscles around a joint; bursae are filled with synovial fluid and are found around almost every major joint of the body; when they become inflamed, the condition is called bursitis....
e permit smooth gliding between bone, muscle, and tendon. They cushion and protect the rotator cuff from the bony arch of the acromion.

Measurement of shoulder loads

For understanding normal and pathologic shoulder function knowledge of forces in the glenohumeral joint is essential. It forms the basis for performing fracture treatment or joint replacement surgery, for optimizing implant design and fixation and for improving and verifying analytical biomechanical models of the shoulder. With instrumented shoulder implants developed at the Julius Wolff Institut (Charité Berlin) the joint contact forces and moments can be measured in vivo during different activities.

Additional images

Medical problems

Shoulder problems
Shoulder problems

Shoulder problems, including pain, are one of the more common reasons for physician visits for musculoskeletal symptoms. The shoulder is the most movable joint in the body....
Rotator cuff tear
Rotator cuff tear

Rotator cuff tears are tears of one, or more, of the four tendons of the rotator cuff muscles.Rotator cuff tears are among the most common conditions affecting the shoulder....

Shoulder

Joints of the shoulder

Glenohumeral joint

Acromioclavicular joint

Sternoclavicular joint

Movements of the shoulder

Major muscles

Rotator cuff

Measurement of shoulder loads

Additional images

Medical problems

See also

External links