ArticlesAnatomyUpper limbShoulder and armClavicle

ArticlesAnatomyUpper limbShoulder and armClavicle

Clavicle

Author: Andrew Lim • Reviewer: Martin Lalama
Last reviewed: September 14, 2023
Reading time: 9 minutes

The clavicle is an elongated, S-shaped bone that rests horizontally at the sternum across the upper part of the ribcage, and the acromial end of the scapula. This bone is an important part of the skeletal system since it plays an essential role in everyday functional movement, serving as the connection between the axial skeleton and the pectoral girdle.

As a result, the clavicle is able to act as a brace for the shoulder, allowing weight to be transferred from the upper limbs to the axial skeleton. Injuries of the clavicle seriously compromise everyday activities.

Key facts
Landmarks	Superior surface: acromial facet Inferior surface: sternal facet, costal tuberosity, conoid tubercle
Muscles	Lateral third: trapezius muscle (posterior surface), deltoid muscle (anterior surface) Medial third: sternocleidomastoid muscle (superior surface), pectoralis major muscle (anterior surface), subclavian muscle (inferior surface - subclavian groove), sternohyoid (medial end of clavicle)
Joints	Acromioclavicular - between acromial head of clavicle and acromion of scapula - ligament: acromioclavicular ligament Sternoclavicular - between sternal end of clavicle and manubrium of sternum - ligaments: sternoclavicular ligaments, anterior and posterior interclavicular ligaments
Clinical relation	Fractures

This article will discuss the anatomy of the clavicle.

Contents

Articulations
1. Acromioclavicular joint
2. Sternoclavicular joint
Bony landmarks
Muscle attachments
Fractures
Sources

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Articulations

Due to the clavicle’s structure, there are only two planar diarthrosis articulations that can be found. This type of articulation is also known as a ‘double plane joint’ – where two joint cavities are separated by a layer of articular cartilage.

Acromioclavicular joint

The first is the acromioclavicular joint, which is formed by the acromial end of the clavicle and the acromion of the scapula respectively. It enables slight gliding movement about the shoulder region. The synovial joint is surrounded by a capsule of articular cartilage filled with intra-articular synovium.

From infancy, the articular cartilage starts off as hyaline cartilage, but soon develops into fibrocartilage (at the scapula acromion and the clavicle acromial end at ages 17 and 24, respectively).The acromioclavicular ligament forms a strong connection between the clavicle and the scapula acromion, which restricts movement about the clavicle at its acromial end.

Sternoclavicular joint

The other is the sternoclavicular joint, which is formed by the sternal end of the clavicle and the manubrium of the sternum. This synovial joint is important as it anchors the clavicle and scapula to the axial skeleton. However the joint enables a variety of limited movements of the arm, including:

protraction and retraction
depression and elevation
slight rotation

Like the acromioclavicular joint, the sternoclavicular joint is surrounded by an articular cartilage capsule, but with a fibrocartilage articular disk inside that creates a clavicular and a sternal synovial cavity. Sternoclavicular joint ligaments stabilize the joint on its anterior and posterior surfaces. The joint is also reinforced by two accessory ligaments:

The anterior interclavicular ligament, which covers the superior surface of the joint. This ligament is responsible for preventing dislocation of the clavicle upon shoulder depression.
The posterior costoclavicular ligament, which runs from the clavicle costal tuberosity to the superior and medial surface of the first rib. In contrast, this ligament prevents clavicle dislocation upon shoulder elevation.

Looking for a new way to learn and revise? Find out how to learn the anatomy of the clavicle while playing games!

Sternoclavicular joint in a human skeleton. Notice how the medial ends of the clavicles articulate with clavicular fossae of the manubrium of sternum.

Bony landmarks

Extremities

The orientation of the clavicle can be distinguished by its ends: a broad, flat acromial end (referred to as the lateral third); and a round pyramidal-like sternal end (referred to as the medial two-thirds). Each end has unique bony landmarks, depending whether the superior or inferior surface of the bone is viewed.

Superior surface

The superior surface of the clavicle has a smooth appearance. The acromial facet can be seen at the far posterior edge of the acromial end. It appears as a small flattened oval surface and enables the clavicle to articulate about the acromion of the scapula in the acromioclavicular joint.

Inferior surface

In contrast, the inferior surface of the clavicle is quite rough and has many prominent lines, indicating sites where muscle and ligaments may attach to the bone. These landmarks include:

The sternal facet, found far at the edge of the sternal end. It is shaped like a triangle, with a posterior tip and an anterior base, and forms the sternoclavicular joint.
The costal tuberosity, located at the sternal end of the bone. It is distinguished as a broad rough surface over 2 cm in length, and is the site where costoclavicular ligament attaches.
The conoid tubercle, which is found more laterally towards the acromial end. It appears as a rough eminence found where the flat portion of the clavicle meets the tip of the pyramidal sternal end. This feature acts as the site where the conoid ligament attaches.
The trapezoid line, which is also near the acromial end of the clavicle, running laterally from the conoid tubercle. It servers as an attachment site for the trapezoid ligament.

Muscle attachments

A total of six muscles are attached to the clavicle, found distributed at either the lateral third or medial two thirds of the bone.

Two muscles are attached to the lateral third of the clavicle:

The trapezius muscle, which is attached along the posterior surface of the bone.
The deltoid muscle, where the anterior portion of the muscle is attached to the periosteum at the anterior surface of the bone.

Four muscles are attached to the medial third of the clavicle:

The sternocleidomastoid muscle, where the muscular clavicular head of the muscle is attached to the superior surface of the bone.
The pectoralis major muscle, which is attached to the anterior surface of the bone.
The subclavius muscle, which is attached to a groove found in the middle of the bone’s inferior surface. From there, the muscle extends into both lateral and medial areas of the clavicle.
The sternohyoid muscle, which attaches to the medial end of clavicle.

Take the quiz below to test your knowledge about the clavicle!

Fractures

Fractures are common pathologies that occur in the clavicle, usually resulting from injury or trauma. This can include car accidents or contact sports, where the clavicle is exposed to strong impacts that can exert compressive forces on the bone. Alternatively, falls can trigger a clavicle fracture, such as falling directly on one’s shoulder, or falling with an outstretched arm. Clavicle fractures can also arise during childbirth, when complications occur as the neonate passes through the birth canal.

Symptoms of a clavicle fracture include:

Severe pain upon movements of the shoulder and arm
Swelling, bruising and tenderness over the fractured area
Sagging of the shoulder in an anterior and inferior direction

Clavicle fractures can be treated either:

Non-surgically, which is the preferred method when the fractured clavicle is still lined up correctly. With a simple arm sling to keep the clavicle pieces in place, the fracture can heal naturally without the need for invasive treatments.
Surgically, which is required when the fractured clavicle pieces are unaligned. With this treatment, the fractured pieces are screwed to a metal plate to keep them in place during the healing process. As the clavicle heals, the metal plate and screws are replaced by pins, which can be removed later in the future.

Sources

All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines.

References:

Tortora GJ, Derrickson B, Tortora GJ. Principles of anatomy and physiology. Hoboken, N.J.: Wiley; 2009. pg: 236, 372-373.
Martini F, Timmons MJ, Tallitsch RB. Human Anatomy: Pearson Benjamin Cummings; 2012. pg: 174, 182, 183, 223, 231, 294.
Saccomanno MF, De Ieso C, Milano G. Acromioclavicular joint instability: anatomy, biomechanics and evaluation. Joints. 2014;2(2):87-92.
Pourcho AM, Sellon JL, Smith J. Sonographically guided sternoclavicular joint injection: description of technique and validation. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 2015;34(2):325-31.
Gray H, Lewis WH. Anatomy of the Human Body: Lea & Febiger; 1918.
Moser T, Lecours J, Michaud J, Bureau NJ, Guillin R, Cardinal E. The deltoid, a forgotten muscle of the shoulder. Skeletal radiology. 2013;42(10):1361-75.
Saha A, Mandal S, Chakraborty S, Bandyopadhyay M. Morphological study of the attachment of sternocleidomastoid muscle. Singapore medical journal. 2014;55(1):45-7.
Hasan SS, Romeo AA. Thoracic outlet syndrome secondary to an anomalous subclavius muscle. Orthopedics. 2001;24(8):793-4.
OTA. Clavicle Fracture (Broken Collarbone): American Academy of Orthopaedic Surgeons - Orthopaedic Trauma Association; 2011 (accessed 15/04/2015).

Illustrators:

Bones of the thorax (cadaveric dissection) - Prof. Carlos Suárez-Quian

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