The sternoclavicular joint or sternoclavicular articulation is a synovial

saddle The 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 kno ...

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, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the r ...

, as well as the first

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

. The joint possesses a joint capsule, and an articular disk, and is reinforced by multiple ligaments.

Structure

The joint is structurally classed as a synovial

plane joint A plane joint (arthrodial joint, gliding joint, plane articulation) is a synovial joint which, under physiological conditions, allows only gliding movement. Plane joints permit sliding movements in the plane of articular surfaces. The opposed sur ...

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

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 clavicle, the clavicular notch (the superior and lateral part of the sternum), and (the superior surface of) the

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck ...

of the

first rib 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 ...

(visible from the outside as the suprasternal notch). 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 In human anatomy, the internal thoracic artery (ITA), previously commonly known as the internal mammary artery (a name still common among surgeons), is an artery that supplies the anterior chest wall and the breasts. It is a paired artery, with one ...

, and of the suprascapular artery. 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 meagre superiorly and (especially) posteriorly, where it consists mostly of loose areolar connective tissue.

Articular disc

The joint features a fibrocartilaginous articular disc 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 Plane(s) most often refers to: * Aero- or airplane, a powered, fixed-wing aircraft * Plane (geometry), a flat, 2-dimensional surface Plane or planes may also refer to: Biology * Plane (tree) or ''Platanus'', wetland native plant * ''Planes' ...

, predominantly in the anteroposterior 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 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 blood vessels from injury. S ...

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 ) is the central compartment of the thoracic cavity. Surrounded by loose connective tissue, it is an undelineated region that contains a group of structures within the thorax, namely the heart and its vessels, the esopha ...

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

Other

In SAPHO syndrome there may be arthropathy of the sternoclavicular joint. Septic arthritis may rarely affect the sternoclavicular joint.

References

External links

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