Clavicle anatomy: where your collarbone is and how it is built

Also called

Collarbone

What it is

The collarbone, an S-shaped long bone running between the sternum and the shoulder.

Location

Lies horizontally at the top of the chest, articulating with the sternum medially and the acromion of the scapula laterally.

Function

Holds the shoulder away from the trunk and transmits forces from the arm to the axial skeleton.

Body system

Skeletal · paired (left and right)

FMA ID

FMA13323 (Foundational Model of Anatomy)

Key facts

• It is the only bony link between the upper limb and the axial skeleton.
• It is the first bone to begin ossifying (about week 5 to 6 of development), mostly by intramembranous ossification. Its medial end fuses last, in the mid-twenties.
• Its subclavian groove gives attachment to subclavius.
• Its medial end forms the sternoclavicular joint, the only joint between the upper limb and the axial skeleton; its lateral end forms the acromioclavicular joint.

Clinical relevance

It is commonly fractured at the junction of its middle and lateral thirds, often after a fall on the shoulder.

The clavicle extends between the manubrium of the sternum and the acromion of the scapula. You can feel it along its whole length just under the skin at the front of the base of the neck, and in slim people it is visible. (TeachMeAnatomy: The Clavicle.)

It lies on the anterior shoulder and is the only long bone in the body that lies horizontally. Together with the scapula it forms the pectoral (shoulder) girdle. (OpenStax Anatomy and Physiology 2e, 8.1: The Pectoral Girdle.)

The name comes from the Latin clavicula, a diminutive of clavis (key), so it means "little key". The usual explanation is that the bone's slender shape with a bent end looks like an old key, or that it turns on its long axis like a key when the arm is raised; this is tradition rather than a settled fact. Anatomical terms built on it include sternoclavicular, acromioclavicular, costoclavicular and coracoclavicular. (University of Iowa, Latin Lovers: Clavicle.)

The clavicle is slender and S-shaped. Seen from the front, its medial part curves forward (convex) and its lateral part curves backward (concave). It is described in three parts: the sternal (medial) end, the shaft and the acromial (lateral) end. (TeachMeAnatomy: The Clavicle.)

The sternal end is rounded and roughly pyramidal, with a triangular facet that joins the sternum. The acromial end is broad and flat, with a small oval facet for the acromion. The upper surface of the bone is smooth; the lower surface is rough and carries most of the landmarks. (Kenhub: Clavicle.)

On the underside, near the sternal end, the costal tuberosity (more than 2 cm long) anchors the costoclavicular ligament. In the middle of the underside, the subclavian groove holds the subclavius muscle. Near the lateral end, the conoid tubercle and the trapezoid line anchor the two parts of the coracoclavicular ligament. (Kenhub: Clavicle.)

The sternoclavicular joint joins the sternal end of the clavicle to the manubrium and the first costal cartilage. It is a saddle-type synovial joint with a fibrocartilage disc that divides it into two compartments. It is the only bony joint between the upper limb and the axial skeleton. (TeachMeAnatomy: The Sternoclavicular Joint.)

The costoclavicular ligament, from the first rib and its cartilage to the underside of the clavicle, is the main stabiliser of the sternoclavicular joint. The anterior and posterior sternoclavicular ligaments and the interclavicular ligament reinforce the capsule. (TeachMeAnatomy: The Sternoclavicular Joint.)

The acromioclavicular joint joins the lateral end of the clavicle to the acromion. It is a plane synovial joint, and no muscle moves it directly; it moves passively as the scapula moves. (TeachMeAnatomy: The Acromioclavicular Joint.)

The coracoclavicular ligament has two parts: the conoid ligament, which runs up from the coracoid process to the conoid tubercle, and the trapezoid ligament, which runs to the trapezoid line. This very strong ligament effectively suspends the weight of the arm from the clavicle. (TeachMeAnatomy: The Acromioclavicular Joint.)

The sternoclavicular joint is classified as a saddle joint and the acromioclavicular joint as a plane joint. (OpenStax Anatomy and Physiology 2e, 9.4: Synovial Joints.)

Six muscles attach to the clavicle. On the lateral third, trapezius attaches to the back edge and the anterior part of deltoid to the front. On the medial two-thirds, the clavicular head of sternocleidomastoid attaches above, pectoralis major in front, subclavius in the subclavian groove below and sternohyoid at the medial end. (Kenhub: Clavicle.)

The clavicle acts as a strut that holds the scapula, and with it the arm, out to the side of the chest. It transmits forces from the upper limb to the axial skeleton and protects the nerves and blood vessels that pass beneath it toward the arm. (OpenStax Anatomy and Physiology 2e, 8.1: The Pectoral Girdle.)

In females the clavicle tends to be shorter, thinner and less curved. In males it is usually heavier and longer, with a greater curvature and rougher surfaces where muscles attach. (OpenStax Anatomy and Physiology 2e, 8.1: The Pectoral Girdle.)

The clavicle is the most commonly fractured bone in the body. Because the sternoclavicular joint is strong and rarely dislocates, a large force through the shoulder usually breaks the clavicle instead, most often between its middle and lateral portions. (OpenStax Anatomy and Physiology 2e, 8.1: The Pectoral Girdle.)

The usual cause is a fall onto the shoulder or an outstretched hand. About 80% of fractures are in the middle third, 15% in the lateral third and 5% in the medial third. (TeachMeAnatomy: The Clavicle.)

The fragments move in a typical way. The weight of the arm pulls the lateral fragment down and pectoralis major pulls it medially, while sternocleidomastoid lifts the medial fragment. This gives the drooping, shortened shoulder seen after a displaced fracture. (TeachMeAnatomy: The Clavicle.)

Symptoms include severe pain on moving the arm, swelling, bruising and tenderness over the bone, and a shoulder that sags forward and down. Fractures whose ends stay aligned are usually treated in a sling; badly displaced fractures may be fixed with a plate and screws. (Kenhub: Clavicle.)

The supraclavicular nerves cross the clavicle and are sometimes cut during surgical repair, which can leave numbness over the upper chest and shoulder. (TeachMeAnatomy: The Clavicle.)

The nearest named structures in the 3D model, measured from the centre of each part:

• Subclavius · muscular
• Trunk of thoraco-acromial artery · cardiovascular
• Subclavian vein · cardiovascular
• Subclavian artery · cardiovascular
• Second rib · skeletal
• Superior intercostal artery · cardiovascular
• Costocervical trunk · cardiovascular
• Suprascapular artery · cardiovascular
• First rib · skeletal
• Transverse cervical artery · cardiovascular