The AC Joint Compression Test

Do You Have a Separated Acromio-clavicular Joint?

Woman with hand on bare shoulder, close-up
Physical Therapy can help if you have shoulder pain.. PhotoAlto/Frederic Cirou/Getty

The acromioclavicular (AC) joint is a part of your shoulder joint that is comprised of the meeting of your collar bone (clavicle) with the acromion process of your shoulder blade.

The AC joint is a very stable joint, and only slight motions occur there.  Still, you can suffer a sprain of the ligaments that hold your AC joint together.  When this occurs, it is called an AC joint separation. This will likely cause significant shoulder pain and you may have difficulty moving your arm normally.

An AC joint separation should not be confused with a shoulder dislocation.  A shoulder dislocation occurs where the ball and socket of your shoulder joint meet.  An AC joint separation occurs on the upper part of your shoulder where your collar bone and acromion process of your scapula meet.

Causes of AC Joint Separation

Since your AC joint is such a stable joint, usually significant trauma is required to cause an injury here.  An AC joint separation typically occurs after a fall onto the side of your shoulder or during a fall on your outstretched hand.

Impact or forces during athletic competition that come from the side or directly in front of your shoulder may also cause an AC joint separation.

Test for an AC Joint Separation

The shoulder special test for an AC joint separation is called the AC joint compression test.  It is a simple test to perform.  Here is how you do it:

  • Sit comfortably in a chair.
  • Have a friend or family member stand to your side where your painful shoulder is.
  • Your friend should place one hand on the front of your shoulder joint and one hand behind your shoulder joint.
  • Finally, your friend should slowly but firmly press on both sides of your shoulder to compress your AC joint.

    A positive test indicating a possible AC joint separation is when extreme pain is elicited in your shoulder.  If your AC joint compression test is positive, you should visit your doctor right away to confirm your suspicions and get you started on the correct treatment right away.

    If you have an AC joint separation, you will likely need to wear a sling on your shoulder while things are healing.  After a few weeks of healing of your AC joint, your doctor may recommend physical therapy to help you improve your shoulder range of motion (ROM) and strength. Your PT can prescribe specific exercises to get your shoulder (and shoulder blade) moving properly.

    Occasionally, surgery is recommended to repair an AC joint separation.  If you have surgery to repair your AC joint, you may also benefit from physical therapy after your surgery to help improve your overall mobility and restore normal shoulder motion and strength. Your PT can also help you manage your shoulder pain after surgery.

    If you have shoulder pain and suspect you have injured your AC joint, the AC joint compression test can help confirm your suspicions.

     If you try the test and feel you have separated your AC joint, visit your doctor to confirm your diagnosis and start the process of healing and recovery.

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