The acromioclavicular (AC) joint is between the upper part of the shoulder blade and the collarbone. AC joint separation happens when the ligaments of this joint become damaged or torn. This causes a separation between the acromion and the collarbone.

Shoulder Anatomy

Causes

This problem is caused by a trauma to the shoulder, such as:

Falling directly onto the shoulder—most common cause
Being hit on the point of the shoulder blade
Falling on an outstretched arm

Risk Factors

Things that may raise the risk of this problem are:

Playing certain sports, such as football, hockey, or lacrosse
Sports that may involve falls like cycling, skiing, or gymnastics
Increased age

Symptoms

Problems may be:

Pain and tenderness over the joint
Swelling
Bruising
A popping feeling in the joint
A bump on the shoulder

Diagnosis

You will be asked about your symptoms, health history, and how the injury happened. An exam will be done. It will focus on the shoulder. This is often enough to make the diagnosis.

Images may be taken of your shoulder. This can be done with x-rays.

Treatment

How long it takes to heal depends on how badly the joint was injured. The goals of treatment are to ease pain and swelling. Medicine can help. Other options are:

A sling to prevent the shoulder from moving and give it time to heal
Ice packs to ease pain and swelling
Exercises to help with strength, flexibility, and range of motion

Surgery

Surgery may be needed if the AC joint separation is severe. Options are:

Trimming back the end of the collarbone so that it does not rub against the shoulder blade
Reconstructing the ligaments that attach to the underside of the collarbone

Prevention

To lower the risk of this health problem:

Do not put yourself at risk for trauma to the shoulder.
Wear safety equipment and use proper techniques when playing sports or doing activities.
Exercise regularly to maintain strength, mobility, and to prevent falls.

RESOURCES:

Ortho Info— American Academy of Orthopaedic Surgeons
http://www.orthoinfo.org

Sports Med—American Orthopaedic Society for Sports Medicine
http://www.sportsmed.org

CANADIAN RESOURCES:

Canadian Orthopaedic Association
http://www.coa-aco.org

Canadian Orthopaedic Foundation
http://www.canorth.org

References:

Acromioclavicular (AC) joint injuries. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/acromioclavicular-ac-joint-injuries. Accessed July 29, 2021.

Shoulder separation. Cedars-Sinai website. Available at: https://www.cedars-sinai.org/health-library/diseases-and-conditions/s/shoulder-separation.html. Accessed July 29, 2021.

Shoulder separation. Ortho Info—American Academy of Orthopaedic Surgeons website. Available at: https://orthoinfo.aaos.org/en/diseases--conditions/shoulder-separation. Accessed July 29, 2021.

Last reviewed July 2021 by EBSCO Medical Review Board Warren A. Bodine, DO, CAQSM
Last Updated: 7/29/2021

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