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The collarbone (clavicle) is a bone that connects the breastbone (sternum) with the shoulder blade (scapula). The collarbone is, anatomically speaking, a part of the chest wall. It functions as a part of the upper limb physiologically, because is involved in the movements of the arm.

There are various conditions that can cause the left and right collarbones to look asymmetrical, but it can also be a normal variation. We are now going to explore some of the possible causes of collarbone asymmetry.

Normal Variations in Collarbone Asymmetry

The left and right sides of the body are not entirely symmetrical, although they seem to be. When you look at your image in the mirror, you will probably not see anything weird as you are used to looking at yourself in the mirror. If you take a look at some other person's mirror image, however, you will certainly notice some asymmetry. A study that examined variations in collarbone asymmetry proved that collarbones are not the exception.

It has been shown that the left collarbone is normally slightly longer and thinner than the right collarbone.

With slight variations, this finding was confirmed in all tested humans regardless of gender.


Osteoarthritis is a degenerative inflammatory disease of the bones and joints. If it affects the collarbone and its joints, it can cause swelling of the joint area. It often occurs in the sternoclavicular joint (the joint that connects the breastbone and the collarbone). Common symptoms include swelling, pain, stiffness, and a cracking noise during movement. The disease can be asymptomatic during the initial phase, with swelling being the only sign. The causes of osteoarthritis include mechanical injury, excess bodyweight, and congenital disorders. As this is a degenerative and progressive condition, the treatment is complex and multidisciplinary.


Osteitis is an inflammation of a bone. Osteitis of the collarbone is not very common, but when it occurs, it can cause pain, restrict movement, and lead to bone enlargement. The cause of this disorder is not yet well investigated.

Mechanical Trauma

An external injury can damage the bone tissue, causing inflammation and hypertrophy of a certain part of the collarbone. Every bone injury should X-rayed as there is always a possibility of fracture. Improper positioning of fractured parts can lead to deformation and collarbone asymmetry.

Chest Wall Deformities

Congenital or developmental deformities of the spine or ribs can cause collarbone deformation. Scoliosis (an abnormal curvature of the spine from side to side) is one of the most common spine deformities that can cause the clavicles to look asymmetrical.


If there is an unusual lump on the clavicle that grows fast and causes pain and discomfort, you should see your doctor in order to rule out the possibility of a malign bone tumor. Although primary tumors of the collarbone are very rare, a bone biopsy should be ordered to check the microscopic features of the lump.

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