Acromioclavicular (AC) Joint Arthritis: Causes, Symptoms, and Treatment

AcromioclavicularAcromioclavicular joint arthritis or AC joint arthritis can be painful and limit the range of motion in the shoulder. It’s the most common type of arthritis found in the older population.

Acromioclavicular joint arthritis is a little hard to pronounce and remember. In fact, it sounds complicated. What is AC joint arthritis? The best way to answer this question is through anatomy.


Three different bones, the collarbone, the shoulder blade, and the arm bone meet to form the shoulder joint. The end of the shoulder blade (scapula) is called the acromion and between this part of the scapula and collarbone (clavicle) is the acromioclavicular joint. When this joint, commonly referred to as the AC joint, wears thin, you can get acromioclavicular arthritis. Arthritis is damage to a joint that can cause inflammation and pain.

Also read: Arthritis in shoulder blades, joints, and arms: Causes, symptoms, and treatment

Is Shoulder Arthritis and AC Joint Arthritis the Same?

Shoulder arthritis and AC joint arthritis are two different conditions. In people who suffer from AC joint arthritis, the junction of the clavicle and acromion wears thin, leading to symptoms of pain, inflammation, and stiffness in the shoulder area. In those who have shoulder arthritis, the arm bone – which is called the humerus, as well as its cartilage – wear away at the socket of the shoulder joint. The treatment and potential complications associated with these two conditions also differ.

What Are the Causes of Acromioclavicular Joint Arthritis?

There are a few AC joint arthritis causes that we can zero in on.

  • Osteoarthritis OA occurs due to gradual wear and tear. Over time, cartilage of the joint can wear away, causing the bone of the joint to scrape together. For some sufferers, pain can be severe.
  • Rheumatoid arthritis RA happens when the immune system attacks the lining of the joint. This can eventually result in bone erosion and joint deformity.
  • Joint injury – A fracture or even a shoulder separation can lead to AC joint arthritis. A shoulder separation damages ligaments around the AC joint. It’s possible that the bones will no longer line up properly and start scraping against each other. This leads to the inflammation and pain that is characteristic of acromioclavicular arthritis.

Also Read : Stiff Joints: Causes, Symptoms, and Treatment

Symptoms of Acromioclavicular Joint Arthritis

AC joint arthritis symptoms usually progress slowly. Sometimes, it can seem as if the discomfort is going away, but then it returns. Pain at the front and top of the shoulder can be AC joint arthritis, but tenderness and pain at the back of the shoulder may be a sign of shoulder arthritis.

Here are the typical symptoms associated with AC joint arthritis:

  • Pain – this is usually at the top of the shoulder; however, it may spread to the side of the neck. For some people, there will be pain with certain motions, such as holding the arm out straight and then moving it in a horizontal fashion across the body, toward the other shoulder. Reaching up to carry out tasks like putting on a car seat belt can be difficult. Reaching behind the back or overhead can also cause pain. It’s important to keep in mind that being inactive can make the condition worse.
  • Swelling – arthritis causes soft tissue to become irritated, so it can swell. Swelling at the top and front of the shoulder can happen to those who suffer from AC joint arthritis, but it doesn’t occur in all cases.
  • Limited motion – having a limited range of motion is not just due to pain, it can be the result of stiffness in the joint area.

AC joint arthritis symptoms can get worse with activities that use the joint. For instance, lifting something might cause pain. Some people who suffer from AC arthritis due to osteoarthritis or rheumatoid arthritis also have symptoms in other joints.

Also Read : Shoulder blade (scapula) pain causes, symptoms, treatments, and exercises

How Is AC Joint Arthritis Diagnosed?

The majority of people who are 50 or older have some signs of osteoarthritis in their major joints. In a lot of cases, it can be seen on an X-ray even when there are no symptoms. So, when it comes to diagnosing AC joint arthritis, while tests like X-rays and MRIs can be helpful, they should just be part of the diagnostic process.

To make a proper diagnosis, the following tools are normally used:

  • Patient discussion – the doctor will ask the patient about work, lifestyle, and various activities prior to the shoulder symptoms arising. Family history will be reviewed and the symptoms, pattern of pain, limitations the patient has as a result of symptoms, as well as what makes symptoms worse will all be discussed.
  • Physical exam – the painful joint will be examined for signs of injury, tenderness, pain, and muscle weakness. Any differences between the affected shoulder and the unaffected shoulder will be noted. The shoulder’s range of motion will also be tested.
  • X-rays – when an x-ray shows that the acromioclavicular joint’s bones are closer together than normal, it could potentially indicate osteoarthritis. An X-ray can also show changes in bones, such as bone spurs.
  • Injection – testing for arthritis can include injecting a local anesthetic into the painful joint. If the patient feels pain relief, a diagnosis of arthritis is usually confirmed.
  • Ultrasound – an ultrasound of the joint is often done at the same time as a diagnostic injection is carried out. The ultrasound is used as a tool to guide the injection.
  • MRI – Magnetic Resonance Imaging can provide images of soft tissue, such as ligaments, tendons, and muscles, as well as bone. This can be helpful when symptoms are due to something other than osteoarthritis. When the AC joint is inflamed, an MRI often shows the excess fluids and swelling around the joint.
  • Bone scan – this is a nuclear medicine imaging procedure that can detect location of bone inflammation and infection, as well as other bone issues, such as cancer.
  • Lab tests – while lab tests can detect AC joint arthritis, they can be used to rule out other problems, including infection or gout, which can also lead to shoulder pain.

Treatment Options for AC Joint Arthritis

Unfortunately, acromioclavicular joint arthritis is a degenerative disease that can’t be reversed. There is AC joint arthritis treatment that can help control the symptoms. Modifying activities and using medications are primary treatments for this condition. When this type of non-surgical treatment for AC joint arthritis is ineffective, surgery is an option.


The following list is an outline of different treatments:

  • Activity modification – some activities will aggravate AC joint arthritis. For example, lifting weights, golfing, and exercising require cross-body arm movement that should be avoided if they lead to pain. Some routine activities may have to be avoided and alternative ways of carrying out tasks may be required.
  • Warm or cold compress – stiff joints can be loosened in some people when they use moist heat. A warming pad or whirlpool before activity can be useful. Icing the shoulder joint for 15 minutes after activity can also help to decrease swelling.
  • Physical therapy – while physical therapy can be effective in cases where people suffer from hip or knee osteoarthritis, many therapists report that physical therapy is less effective for acromioclavicular patients. Having said this, some AC joint arthritis patients do find that carefully stretching and strengthening muscles can be helpful. In other words, AC joint arthritis physical therapy can’t always be completely ruled out.
  • Rest – initial treatment is often resting the shoulder; however, staying still for too long can lead to stiffness and a lack of range of motion.
  • Over-the-counter medications – rest is often accompanied by over-the-counter or prescription anti-inflammatory medication. Other medications, such as corticosteroid injections, are options a doctor can explain to an AC joint arthritis sufferer.
  • Surgery – the preferred AC joint arthritis surgery is acromioclavicular joint arthroplasty. This involves removing part of the collarbone that is worn out. The scar tissue left as a result of the procedure can prevent further abrasion of the bone. The procedure can be carried out on an outpatient basis. Recovery from this surgery usually takes about three months.

Treating acromioclavicular joint arthritis isn’t quick and easy. However, sufferers should not give up after trying just one treatment that fails. A lot of people who have AC joint arthritis end up needing at least two treatments to gain pain relief and resume some level of normal activity. Rather than taking matters into your own hands, talk to your doctor about treatment options if you suspect you have this form of arthritis or have been diagnosed with it.

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Author Bio

Emily Lunardo studied medical sociology at York University with a strong focus on the social determinants of health and mental illness. She is a registered Zumba instructor, as well as a Canfit Pro trainer, who teaches fitness classes on a weekly basis. Emily practices healthy habits in her own life as well as helps others with their own personal health goals. Emily joined Bel Marra Health as a health writer in 2013.


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