The Symptoms and Treatments of AC Joint Pain

The shoulder joint is a complex joint that joins together three bones. Most people think the shoulder is the ball-and-socket joint where the top of the arm bone meets the shoulder blade (the so-called glenohumeral joint). However, there is another important joining of two bones in the shoulder: the junction of the collarbone and the shoulder blade (the acromioclavicular joint).

A woman undergoing a shoulder exam
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The acromioclavicular joint, abbreviated as the AC joint, is the junction of the end of the collarbone (clavicle) with the side of the shoulder blade (called the acromion). The AC joint can be damaged much like other joints and may require treatment. One treatment used for degenerative AC joint problems (such as arthritis) is to remove the end of the clavicle so that the bones are not rubbing against each other. This surgery is called a distal clavicle resection (or distal clavicle excision) and is often referred to as a Mumford procedure.

AC Joint Problems

There are three primary reasons why people have chronic, long-standing problems with the AC joint:

  1. Degenerative arthritis (osteoarthritis)
  2. Post-traumatic arthritis
  3. Distal clavicle osteolysis

There are also times the AC joint can be problematic in an acute (sudden injury) setting, but when talking about removing the end of the collarbone, generally this is a surgery reserved for people with more long-standing problems with the AC joint. That said, acute injuries can develop into post-traumatic arthritis, one of the reasons a Mumford procedure may be considered.

Degenerative arthritis occurs when there is slowly developing wear and tear to the cartilage of the AC joint. Over time, as the smooth cartilage surface wears away, exposed bone and bone spurs may develop around the AC joint. Even though this particular part of the shoulder joint doesn't move much, even subtle motion in an arthritic joint can cause pain.

Post-traumatic arthritis means that some injury occurred that led to the development of a more rapidly progressing cartilage and joint problem. The symptoms of exposed bone and bone spurs may be the same as osteoarthritis, but the development of the injury is different. Post-traumatic arthritis of the AC joint can occur after distal clavicle fractures and shoulder separation injuries.

Distal clavicle osteolysis is an overuse syndrome, commonly seen in weight lifters. Exactly what leads to the development of bone weakening at the end of the clavicle is unclear, but this syndrome is frequently seen in weightlifters who are doing overhead lifts. Sometimes rest and conservative treatment can bring relief of symptoms, but this condition can also lead to more chronic pain in the AC joint.

Signs of AC Joint Problems

The most common sign of a problem with the AC joint is pain located directly at the junction of the end of the collarbone and the top of the shoulder blade. Sometimes the pain can radiate up the base of the neck or down the arm. Muscular pain in the trapezius and deltoid muscles is a common symptom of an AC joint problem. Pain symptoms usually worsen with movement of the shoulder.

Simple movements that tend to aggravate AC joint problems are reaching across the body, such as to wash your opposite shoulder or armpit. Reaching behind yourself to buckle a seatbelt or fasten a bra can also elicit painful symptoms.

More strenuous sports activities such as a bench press or overhead press in the weight room can especially aggravate AC joint problems. Pain at night (so-called nocturnal pain) is also a problem, especially when people roll to their affected side. This pain can often awaken people from sleep as they roll on to the painful shoulder.


The diagnosis of an AC joint problem can be made by taking a careful history of the patient's symptoms and examining the affected shoulder. Pain is most prominent directly over the AC joint.

A cross-arm adduction test is performed by taking the affected arm straight across the body and pressing towards the opposite shoulder. A positive test recreates symptoms of pain directly at the AC joint. Many people with AC joint problems also have typical symptoms of rotator cuff impingement, since these conditions go hand in hand.

Tests performed to identify AC joint problems typically start with X-rays. X-rays can show wearing out of the AC joint, with narrowing of the space between the end of the collarbone at the shoulder blade. Bone spurs may also be evident on an X-ray image.

If the X-ray does not clearly show a problem, or if there is a question of other damage (such as a rotator cuff tear), an MRI test may be performed. The MRI can show in more detail the condition of the bone, cartilage, ligaments, and tendons around the shoulder.

If there is still a question whether the AC joint is a source of pain, a simple injection of anesthetic into the AC joint should completely relieve symptoms. If the joint is anesthetized, and the pain is completely relieved through the aforementioned tests and maneuvers, then the AC joint is likely the source of the problem.

Non-Surgical Treatment Options

A distal clavicle resection is almost always the last in a long series of non-invasive treatments. The usual treatments for AC joint pain include the following.

  • Rest: Allowing the stress on the joint to subside, especially in very active individuals who may have been aggravating the problem. Rest does not necessarily mean you have to be completely sedentary, but it typically does mean avoiding specific activities that seem to elicit the most painful symptoms.
  • Oral anti-inflammatory medications: Oral anti-inflammatory medications, often called NSAIDs, are helpful to quiet down inflammation and relieve pain coming from the AC joint. While usually not a great long-term solution, these medications can often be helpful for settling down the inflammation and quieting a flare-up of symptoms.
  • Physical therapy: Physical therapy can help to improve the mechanics of the shoulder and take the stress off the AC joint. As mentioned before, part of the AC joint is the shoulder blade, and poor mechanics or mobility of the shoulder blade can exacerbate symptoms of an AC joint problem.
  • Cortisone injections: Cortisone is a powerful anti-inflammatory medication that, when injected directly into the AC joint, can settle down symptoms of inflammation very quickly. While the effects of a single injection wear off within weeks or months, often the pain can remain under control for a much longer time period.

If all of these treatments fail to provide lasting relief, and your symptoms are preventing you from doing the activities you want and need to be able to do, then surgery may be considered.

Mumford Procedure

One surgical option is to remove the damaged end of the collarbone, a surgery referred to as a Mumford procedure or distal clavicle excision. E.B. Mumford was the first surgeon to describe this technique in the early 1940s, and therefore his name was given to the procedure. This surgery can also be performed in conjunction with other surgical procedures of the shoulder, including rotator cuff repairs or subacromial decompression.

A Mumford procedure can either be performed through a small incision or as part of arthroscopic shoulder surgery. During the surgery, the end of the collarbone is removed. Approximately 1 cm of the clavicle is typically removed; taking too much or too little can both cause problems. The advantage of arthroscopic surgery is its minimally invasive nature, whereas the disadvantage is that it can be more difficult to judge if the proper amount of bone is removed. Both open and arthroscopic methods are effective in treating this condition.

Rehabilitation following a Mumford procedure may vary, especially if there were other procedures (such as rotator cuff repair) performed during the same operation; as always, check with your surgeon on the specific protocol for rehab he or she wants you to follow.

After an isolated Mumford surgery, rehab can begin fairly quickly. Following a brief period of immobilization in a sling (often days or a week), gentle movements of the shoulder can begin. It is important to try to move the shoulder early after surgery to prevent development of stiffness or a frozen shoulder. Once range of motion is recovered, a strengthening program can begin.

Usually, full activities are resumed about six to eight weeks following surgery, although strenuous weight-lifting activities may take longer to return.

Risks of Surgery

Historically, damage to the attachment of the deltoid muscle on the scapula and collarbone was once a big concern. Because the surgical approach to the AC joint required at least partial detachment of the muscle, recovery of normal shoulder function could take a long time. With arthroscopic techniques, the muscle attachments are not disrupted, and this complication is much less of a concern.

In addition to these specific risks, other possible complications include infection, stiffness of the shoulder, or persistent pain. Other potential problems include recurrence of symptoms or even, in rare cases, instability of the collarbone. Adherence to specific instructions from your surgeon, specifically about when to begin moving your shoulder, can help to ensure the best chance of a full recovery.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.