What Type of Joint Is the Sternoclavicular Joint?

The sternoclavicular joint (SCJ) connects the collarbone (calvicle) to the large bone that runs down the center of the chest (sternum). Two SC joints, one on the left side of the body and one on the right, connect the arm and shoulder bones to the vertical skeleton. They also support the shoulders. Tough, fibrous bands (ligaments) hold the SC joints in place.

Joint of the Upper Limb

• The sternoclavicular joint is an upper limb joint. The collarbone (clavicle), along with the shoulder blade (scapula), connect the arms (upper limbs) to the trunk of the body.

Synovial Joint (Diarthroses)

• Two bones, with ends covered with smooth, white, hyaline cartilage, make up synovial joints. Hyaline cartilage has a rubbery texture that helps the bones to slide against each other smoothly. The joint space is enclosed with a fibrous capsule, lined with synovial membrane. The membrane produces synovial fluid; it fills the cavity in the joint and acts as a shock absorber. Synovial fluid also lubricates and nourishes the hyaline cartilage. The design of a synovial joint allows for fairly free movement.

Biaxial

• Biaxial joints, such as the SCJ, move in two planes (axes) at right angles to each other. Biaxial joints allow so much movement that they appear to move in all directions, similar to a multiaxial joint.

Saddle Type

• The SCJ is a biaxial, saddle-type joint. One bone of the joint is concave, like the shape of a saddle. The other bone is convex, like a horse rider sitting in the saddle.