AC Joint Dislocation

AC Joint Dislocation

Is a shoulder separation the same as a shoulder dislocation? No!

These two injuries are commonly confused, but they are very different conditions.

A shoulder separation is an injury to the ligament (the fibrous connective tissue that connects bone to bone) between the shoulder blade and collarbone. A shoulder dislocation occurs when the collarbone (clavicle) detaches from the bony tip of the outer edge of the shoulder blade (acromion). In layman’s terms, it’s when the top of the arm bone loses contact with the shoulder blade socket.

Not only are the injuries different in anatomical terms, but the treatment, recovery, and complications are also different.

What Causes AC Joint Dislocation?

Many things can happen to the AC joint, but the most common conditions are arthritis, fractures, and separations. Arthritis is a condition where there is a loss of cartilage in the joint – essentially, wear and tear of the smooth cartilage that allows the bones to move smoothly. Like arthritis in other joints in the body, it is characterized by pain and swelling, especially with activity. Over time, the joint can wear out, with spurs forming around it. These spurs are a sign of arthritis, not the pain’s cause.

Reaching across the body toward the other arm aggravates arthritis at the AC joint. AC joint wear and tear is common in weightlifters, especially those who bench press and, to a lesser extent, military press. In weightlifters, arthritis at the AC joint has a special name — osteolysis.

The most common cause of AC (Acromioclavicular) joint dislocation is a fall onto the shoulder, injuring the surrounding ligaments that stabilize the joint. If the force of the fall is severe, the ligaments attached to the underside of the collarbone are torn, causing dislocation of the shoulder blade and the collarbone. Some of the causes of AC joint dislocation include:

  • A direct blow to the joint.
  • Heavy fall onto the tip of the shoulder or top of the shoulder.
  • Fall on an outstretched hand.
  • Arthritis of the joint.
  • Lifting heavy objects, such as weightlifting.
  • Repetitive overhead activity.
  • Sports injury, such as contact sports.
  • Fractures.

Types of AC Joint Dislocation

The type of AC joint dislocation depends upon the extent of the tear of the acromioclavicular or coracoclavicular ligaments that secure the AC joint in place. The common types of AC joint dislocation include:

  • Type 1: The acromioclavicular ligament is slightly torn, but there is no damage to the coracoclavicular ligament.
  • Type 2: The acromioclavicular ligament is totally torn, but there is a slight or no tear to the coracoclavicular ligament.
  • Type 3: Both the acromioclavicular and coracoclavicular ligaments are totally torn. In this scenario, the clavicle separates from the end of the shoulder blade (scapula).

Signs and Symptoms of AC Joint Dislocation

AC joint injury pain is often felt radiating to the neck and the deltoid muscle (the muscle forming the rounded contour of the shoulder – also known as the common shoulder muscle). The AC joint may also become swollen, and the upper part is often held in adduction (moving it back toward your center) with the acromion depressed, which may cause the clavicle to be elevated. Further signs and symptoms may include:

  • Pain.
  • Joint instability.
  • Restricted range of motion.
  • Swelling.
  • Bruising.
  • Tenderness.
  • Weakness in the arm or shoulder.


Your symptoms and medical history will be reviewed for an accurate diagnosis, and a thorough physical examination will be performed to check for range of motion, stability, and joint strength. If necessary, certain imaging tests such as X-rays, MRIs, CT scans, or ultrasounds may be ordered for a detailed evaluation of the joint and surrounding soft tissue structures to confirm the diagnosis.


Shoulder X-rays are necessary to confirm the diagnosis and make sure that a clavicle fracture isn’t present. Unless an AC Joint injury occurs in a young manual laborer or an overhead athlete, it’s often best to wait for at least three months before considering any surgical reconstruction, even in a professional (non-overhead) athlete.


Conservative treatment is usually effective, but surgery is required in cases of a severely unstable joint.

Non-surgical Treatments

Non-surgical options for treatment include:

  • Medications: Over-the-counter anti-inflammatory pain medications like ibuprofen (Advil, Motrin) or naproxen (Aleve) can reduce swelling and pain.
  • Rest: Avoid activities that cause pain and use a sling to immobilize your shoulder and arm.
  • Ice: An ice pack can be applied for 15-20 minutes at a time to reduce swelling and pain.
  • Physical therapy: Specific exercises can help strengthen the shoulder muscles.

Most people can return to their normal function and contact sports after conservative treatment within three months with either few or no symptoms.

Surgical Treatment

Surgery may be an option if pain persists, or you have a severe separation. Most people with AC joint injuries can be treated without surgery.

The exceptions are:

  1. When the dislocated clavicle is extremely high.
  2. If the clavicle has been forced too far backward.
  3. If the clavicle has been forced too far downwards.

Although these circumstances are uncommon, they do occur. They are a good reason to have any AC joint injury evaluated by a physician who may recommend trimming the end of the clavicle to prevent it from rubbing against the acromion.

If a significant deformity is noted, your surgeon may recommend reconstructing the ligaments that attach to the underside of the clavicle. This anatomic reconstructive surgery can be performed either arthroscopically or as open surgery. It repairs and reattaches torn ligaments and stabilizes the bones with or without the help of fixation devices, such as plates.

Surgery is followed by rehabilitation to restore motion, flexibility, and strength.

After Surgery and Rehabilitation

Postoperative rehabilitation typically includes using a shoulder sling for six weeks, followed by physical therapy for three months. This helps restore movements and improve strength. You may be able to return to sports in 5-6 months after surgery.

Motion, strength, and flexibility are the keys to a successful recovery. Most people can return to near full function after this injury, even if there is a persistent, significant deformity. Some people experience pain in the AC joint, even with a mild deformity. This may be due to the development of arthritis, abnormal contact between the bone ends when the joint is in motion, or injury to the cartilage found between the bone ends of the joint.

If you don’t need surgery, range-of-motion exercises should be started as pain eases, followed by a strengthening program. Full recovery can take up to six weeks for Type II separations and up to twelve weeks for Type III separations. Since there is little danger of worsening the condition, you can usually do whatever activities you can tolerate.

After surgery, you may need to wear a sling to support and protect the shoulder for a few days. Your doctor and a physiotherapist will create a custom physical therapy recovery program. You will usually wait four weeks before starting range-of-motion exercises.

You will usually begin with passive exercises where the shoulder joint is moved, but your muscles stay relaxed. Your physiotherapist helps to gently move your joint and gradually stretch your arm. You may be taught how to do passive exercises at home.

Active therapy typically starts six to eight weeks after surgery once the ligaments have healed. Active range-of-motion exercises help you regain shoulder movement using your own muscle power. You might begin with light isometric strengthening exercises and gradually move on to more active strengthening exercises.

Recovery from shoulder surgery can take some time. You will need to be patient and closely follow your physiotherapy program.

Next Steps

Acromioclavicular joint dislocation can be complicated. Choosing the right practice is important. Dr. Peter Howard and his team have both the talent and experience to offer you the best AC joint treatment available. So, if you’re having signs and symptoms of AC Joint Dislocation, call for an appointment with Dr. Peter Howard to have it checked.