AC Joint Separation Management

Acromioclavicular (AC) joints are easily injured and susceptible to secondary issues such as arthritis, laxity, and shoulder pain.  Often referred to as a “separated shoulder,” an AC separation occurs when the ligaments that stabilize the collar bone (clavicle) and the shoulder blade (scapula) are damaged.

The acromioclavicular joint connects the lateral end of the clavicle (collar bone) and the lateral end of the scapula (shoulder blade).  This bony section of the scapula is referred to as the acromion. The AC joint creates a stabilizing union between the front and back of the shoulder girdle.  It’s important to note that when healthy, this joint has ample mobility that allows for significant motion of the shoulder.  The AC joint forms an important archway that protects the rotator cuff and shoulder joint below.

Stabilized by a joint capsule, the acromioclavicular joint encompasses the ends of the clavicle and acromion along with several ligaments. Because ligaments attach bones to bones, when the AC joint ligaments (located under the clavicle) are damaged due to a separated shoulder, there is a downward pull to the clavicle and AC joint.

What Causes a Sprained AC Joint?

Falls are a main cause of separated shoulder injuries.  The AC joint is not overly stable, and its location makes it quite vulnerable to injury.

The two most common injury mechanisms are:

  • Landing on the lateral part of the shoulder, forcing the shoulder downward
  • Landing on an outstretched arm or elbow, forcing the shoulder joint upward into the undersurface of the acromioclavicular joint

Either of these situations noted above will disrupt the AC joint capsule and compromise the stabilizing ligaments.  The grade, or degree, of separation depends on the level of damage to both the ligaments and capsule.

Grades of Separation

Shoulder Separation, Grade I

Mild disruption of the AC joint capsule, resulting in minimal joint instability

Shoulder Separation, Grade II

Moderate disruption of both the AC joint capsule and stabilizing ligaments, resulting in moderate AC joint instability.  Partial tears of both the AC joint capsule and stabilizing ligaments are present.  Holding a weighted object with the injured arm at one’s side will present moderate AC joint laxity with visible elevation of the outer clavicle. The amount of elevation with a Grade II AC sprain is typically ½ to 1 inch, when compared bilaterally.

Shoulder Separation, Grade III

Significant disruption of both the AC joint capsule and stabilizing ligaments results in significant AC joint instability.  Complete tears of the AC joint capsule, and possibly complete tears of at least some of the stabilizing ligaments, are present. When the injured arm rests at the side of the body, there is visible laxity of the acromioclavicular joint and visible elevation of the outer clavicle.  When the arm reaches across the body toward the back of the other shoulder, abnormal lateral clavicle elevation increases.

AC Sprains Grade IV to VI are much more severe and based on the hyper-mobility of the acromioclavicular joint.

Signs & Symptoms of an AC Joint Sprain

  • Pain and localized swelling on the top of the shoulder at the acromioclavicular joint
  • Swelling and/or bruising on the top of the shoulder
  • An obvious bony lump on the top of the shoulder, which is the end of the displaced collarbone (the higher the grade of shoulder separation, the larger the elevation of the outer tip of the clavicle)
  • Limited range of motion (ROM) and pain when lifting the arm
  • With Grade II and Grade III AC joint sprains, a “clicking” or shifting felt in the AC joint with shoulder motion
  • Significant AC pain with active motion (personally moving the arm) or passive motion (someone else moving the arm), horizontally across the body toward the back of the other shoulder

Treating a Separated Shoulder

  • Ice the top and front of the shoulder with the elbow flexed to approximately 90 degrees and supported.
  • Use an arm sling if pain or clicking occur when walking.  This helps to support the weight of the arm while also restricting motion.
  • Once a fracture is ruled out, initiate early motion to reduce stiffness and pain.  Avoid horizontal adduction motion (horizontal movement of the arm across the midline of the body) until pain-free motion is achieved.
  • Perform easy pendulum swings to help regain motion of the shoulder.
  • Initiate a shoulder strengthening program early on with a Grade I & II sprain, if tolerable.  Start with rotational motions and progress with overhead lifts, continuing to avoid horizontal adduction as long as possible.

Ask the Right Questions Like a Pro

As always, my goal is to help you get back in the game as quickly as possible while ensuring a safe return.  Ask the following questions—the same ones smart professional athletes with a separated shoulder would ask their sports medicine specialist—so you too can recover quickly and safely:

1. What grade is my shoulder separation?

2. Do you think I can successfully rehab this AC joint sprain and avoid surgery?

3. Are special padding, taping, or sports equipment alterations needed to reduce the chance of reinjuring my acromioclavicular joint?  Which specific lifts, activities, and motions should I avoid to help my AC joint separation heal quickly?

Sports Medicine Tips For an AC Joint Separation

  • No Need for the Knife – AC joint surgeries are not overly common unless instability is severe or complex limitations are present.
  • Sleep Well? – Plan to avoid sleeping on the injured shoulder for a while.  I severely separated my right AC joint in a winter mountain bike race on a ski slalom course (I know, not the smartest thing that I’ve ever done, but it sure was fun…until I crashed!) in Vermont in 1994. I still can’t sleep on that side!
  • Prioritize Posture – Any position, movement or activity that rounds your shoulders will worsen the pain. It’s that simple.
  • Ice, Motion, Ice – Ice it, move it (in pain-free directions) and then ice it again. It’s a simple formula with fast results.
  • Exercise Efficiently – While sitting or standing tall, relax your arms while squeezing your shoulder blades (scapula) together and exhaling hard.  Hold for 2 seconds and repeat 10 times.  Do this drill as much as possible to stretch out your chest muscles, strengthen your shoulder stabilizing muscle and, most importantly, decompress your AC joint.