AC Separation Causes, Symptoms & Treatment Options

Overview

The acromioclavicular joint (AC joint) is formed where the clavicle (collarbone) meets the acromion(tip of shoulder blade). A capsule and two key ligaments stabilize this joint. An acromioclavicular joint injury typically results from a direct impact to the shoulder. Depending on the ligament damage, the shoulder separation may range from mild to severe, known as the degree of  AC separation.

An AC separation can occur in six different degrees:

• Type I: The AC ligament is sprained or slightly torn but still intact. The joint may be slightly out of place. This is the most common type of shoulder separation.
• Type II: The AC ligament is torn completely through, but the coracoclavicular ligaments remain unharmed.
• Type III: The AC joint is completely separated. Both the AC ligament and the coracoclavicular ligament are torn. The collarbone injury may cause visible elevation.
• Type IV–VI: These rarer and more serious acromioclavicular joint injuries involve severe displacement or tearing.

What causes AC Separation?

AC separations are usually the result of traumatic events, such as falling directly on the shoulder or landing on an outstretched arm.

• How the Injury Occurs: The injury occurs when sudden force or trauma pushes the shoulder downward or backward, tearing or stretching the AC ligaments.
• Common Everyday Causes: Falling on a slippery surface, tripping while walking, or accidentally bumping the shoulder can also cause AC separations in daily life.

AC separations and collarbone injuries are common in:

• Cycling: Falls or collisions can directly impact the shoulder, stressing the AC joint.
• Football: Tackles and falls place sudden force on the shoulder, leading to separation.
• Hockey: Body checks and collisions can cause direct trauma to the collarbone and AC joint.
• Volleyball: Awkward falls or landing on the shoulder after a jump may damage ligaments.

Symptoms

AC joint injury symptoms and their severity in a shoulder separation depend on the grade of the injury. If you have an AC separation, you may experience one or more of the following:

• Tenderness and pain when touching the joint: The area around the AC joint is often sore and sensitive.
• A bump on the top of the shoulder where the clavicle ends: The displaced collarbone may create a visible lump.
• Swelling in the shoulder: Inflammation and fluid buildup can make the shoulder appear puffy or enlarged.

Non-operative treatment

Lower-grade shoulder separations (type I–III) are usually managed with non-operative methods. Common treatments for AC separations include:

• Placing the arm in a sling: Limits movement and allows the shoulder to rest and heal.
• Icing the area: Reduces swelling and helps relieve AC joint shoulder pain.
• Anti-inflammatory medications: Control inflammation and ease discomfort.
• Physical therapy: Restores range of motion, strengthens shoulder muscles, and supports recovery.

Once swelling and pain improve, a structured rehabilitation program is recommended to ensure full recovery and restore proper shoulder function after the collarbone injury.

Try these exercises to help address your condition:

Below is a PDF of the Exercise Program

AC Separation

Surgical Treatment

If you experience a higher grade AC separation (Type III-VI) or if your injury is not improving with non-operative treatments, you may require surgery. The goal of surgical treatment for AC separations is to carefully place the joint back into its original position and, if necessary, repair torn ligaments. This surgery is often done through an open incision and often requires a graft to reconstruct the torn ligaments. Occasionally, it can be done arthroscopically.