The sternoclavicular joint or sternoclavicular articulation is a synovial

saddle A saddle is a supportive structure for a rider of an animal, fastened to an animal's back by a girth. The most common type is equestrian. However, specialized saddles have been created for oxen, camels and other animals. It is not know ...

joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

between the manubrium of the sternum, and the

clavicle The clavicle, collarbone, or keybone is a slender, S-shaped long bone approximately long that serves as a strut between the scapula, shoulder blade and the sternum (breastbone). There are two clavicles, one on each side of the body. The clavic ...

, and the first

costal cartilage Costal cartilage, also known as rib cartilage, are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, pr ...

. The joint possesses a

joint capsule In anatomy, a joint capsule or articular capsule is an envelope surrounding a synovial joint.articular disc The articular disc (or disk) is a thin, oval plate of fibrocartilage present in several joints which separates synovial cavities. This separation of the cavity space allows for separate movements to occur in each space. The presence of an articul ...

, and is reinforced by multiple ligaments.

Structure

The joint is structurally classified as a synovial

saddle joint A saddle joint (sellar joint, articulation by reciprocal reception) is a type of synovial joint in which the opposing surfaces are reciprocally concave and convex. It is found in the thumb, the thorax, the middle ear, and the heel. Structure I ...

and functionally classed as a diarthrosis and multiaxial joint. It is composed of two portions separated by an

articular disc The articular disc (or disk) is a thin, oval plate of fibrocartilage present in several joints which separates synovial cavities. This separation of the cavity space allows for separate movements to occur in each space. The presence of an articul ...

fibrocartilage Fibrocartilage consists of a mixture of white fibrous tissue and cartilaginous tissue in various proportions. It owes its inflexibility and toughness to the former of these constituents, and its elasticity to the latter. It is the only type of ...

. The joint is formed by the sternal end of the

, the clavicular notch of the

sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...

, and (the superior surface of) the

of the

first rib The rib cage or thoracic cage is an endoskeletal enclosure in the thorax of most vertebrates that comprises the ribs, vertebral column and sternum, which protect the vital organs of the thoracic cavity, such as the heart, lungs and great vessel ...

. The articular surface of the clavicle is larger than that of the sternum, and is invested with a layer of cartilage, which is considerably thicker than that of the sternum. The joint receives arterial supply via branches of the

internal thoracic artery The internal thoracic artery (ITA), also known as the internal mammary artery, is an artery that supplies the anterior chest wall and the breasts. It is a paired artery, with one running along each side of the sternum, to continue after its bifurc ...

and 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 ...

. It is innervated via the medial supraclavicular nerve (superficially), and the nerve to subclavius (deeply).

Joint capsule

The joint capsule is thickened anteriorly and posteriorly, but is thinner superiorly and (especially) inferiorly, where it consists mostly of

loose areolar connective tissue Loose connective tissue, also known as areolar tissue, is a cellular connective tissue with thin and relatively sparse collagen fibers. They have a semi-fluid matrix with lesser proportions of fibers. Its ground substance occupies more volume ...

Articular disc

The joint features a

fibrocartilaginous Fibrocartilage consists of a mixture of white fibrous tissue and Cartilage, cartilaginous tissue in various proportions. It owes its inflexibility and toughness to the former of these constituents, and its Elasticity (physics), elasticity to the ...

, which completely divides the joint to form two articular compartments. The disc acts to increase the range of movement of the joint.

Ligaments

The joint is reinforced by two intrinsic and two extrinsic ligaments. The costoclavicular ligament is the main limitation to movement, and therefore the main stabilizer of the joint. * Anterior sternoclavicular ligament (intrinsic) * Posterior sternoclavicular ligament (intrinsic) * Costoclavicular ligament (extrinsic) * Interclavicular ligament (extrinsic)

Function

The sternoclavicular joint allows movement of the

in three planes, predominantly in the

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

and vertical planes, although some rotation also occurs. A description of movement would be elevation and depression. Muscles do not directly act on this joint, although almost all actions of the shoulder girdle or the scapula will cause some motion at this articulation. The unique double-hinged articular disk found at the junction of the clavicular head and

manubrium The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, human lung, lungs, and ma ...

allows for movement between the clavicle and the disk during elevation and depression of the scapula. This disk also allows motion between the sternum (manubrium) and itself during protraction and retraction of the scapula.

Clinical significance

Dislocation

Sternoclavicular dislocation is rare, but may result from direct trauma to the clavicle or indirect forces applied to the shoulder. Posterior dislocations deserve special attention, as they have the potential to be life-threatening because of the risk of damage to vital structures in the

mediastinum The mediastinum (from ;: mediastina) is the central compartment of the thoracic cavity. Surrounded by loose connective tissue, it is a region that contains vital organs and structures within the thorax, mainly the heart and its vessels, the eso ...

; surgery can be used to fix such dislocations, as they are unlikely to heal by themselves. A spontaneous partial dislocation may also sometimes occur.

Other

SAPHO syndrome SAPHO syndrome includes a variety of inflammatory bone disorders that may be associated with skin changes. These diseases share some clinical, radiologic, and pathologic characteristics. An entity initially known as chronic recurrent multifocal ...

there may be arthropathy of the sternoclavicular joint.

Septic arthritis Acute septic arthritis, infectious arthritis, suppurative arthritis, pyogenic arthritis, osteomyelitis, or joint infection is the invasion of a joint by an infectious agent resulting in joint inflammation. Generally speaking, symptoms typica ...

may rarely affect the sternoclavicular joint.

References

External links

Overview at ouhsc.edu
* {{Authority control Joints Thorax (human anatomy)