Sources of AC Joint Pain

Pain in the shoulder's acromioclavicular (AC) joint is a common problem that can be severe and persistent enough to interfere with your daily routine. There are several causes for AC joint pain, and treatment varies depending on what's making your shoulder hurt.

The AC joint is where the acromion (the tip of your shoulder blade—scapula) meets your clavicle (collarbone). "AC" is short for "acromioclavicular," which describes those two bones. Cartilage (flexible but tough tissue) forms a cushion between them. A thin layer of synovial fluid also helps lubricate the joint.

This article will look at the sources of AC joint pain and how the discomfort can be treated and managed.

What Does AC Joint Pain Feel Like?

AC joint pain is an ache at the top of the shoulder that may be accompanied by tenderness. It can be hard to do the things you're used to doing because movements like putting on a seat belt or reaching for something high up can be painful.

Symptoms can depend on the cause but include:

• Shoulder pain: May increase during activities like moving your arm horizontally across your body or reaching up
• Pain: May wake you if you are sleeping on the side with the affected shoulder
• Arm stiffness: Especially felt if you've been inactive
• Clicking or popping sounds when you move your shoulder, called crepitus
• Weakness in your shoulder and arm
• Soreness to the touch

You may also see bruising, bumps, a shoulder that seems to have moved upward, and swelling.

Sources of AC Joint Pain

The source of AC joint pain typically is due to either arthritis or an injury. The symptoms can be similar.

Arthritis

Arthritis is the most common source of AC joint pain. Over time, the cartilage that cushions the joint wears away. When the bones rub against each other, it inflames the joint, causing pain, swelling, and tenderness, especially with activity.

Eventually, bone spurs may develop, which are growths of bone that jut out from the joint. The joint may also become larger.

Injury

AC joint injuries are most common in people between ages 20 and 30, especially among active adults who participate in contact sports, bodybuilding, construction, or other strenuous activities that make shoulder injuries more likely.

Sprains, tears, and separations of the ligaments that hold the joint together are the most common types of AC joint injury. They usually follow a direct hit or fall onto the shoulder. These injuries range from minor to incapacitating.

Two ligaments may be involved: the AC ligament and the coracoclavicular (CC) ligament. AC joint injuries are divided into categories by severity, as follows:

• Type 1: Ligaments surrounding your AC joint have been stretched or sprained but not torn.
  
• Type 2: AC ligament is torn, and there's minor damage to the CC ligament, but it isn't torn.
  
• Type 3: Both ligaments are torn so that the collar bone is separated from the shoulder blade.

There are also types 4 through 6 that are rare and involve more severe injuries, including extensive damage to surrounding tissue.

It's also possible to fracture your collarbone (clavicle), leading to AC joint pain. Shoulder blade (scapula) fractures are less common.

Will Joint Pain Ever Go Away?

AC joint pain from arthritis tends to come and go but generally worsens over time. In the case of injury to the AC joint, rest and treatment can help the injury heal, relieve pain, and restore range of motion. It is possible to completely recover from an AC joint injury, though there may also be some residual pain or loss of range of motion.

Treatment

There are measures you can take to manage your AC joint pain.

For arthritic AC joints:

• Modify or reduce activity to minimize irritating the joint.
• Use a warm, moist compress.
• Alternatively, ice the shoulder. Do not put the ice directly on your skin.
• Physical therapy may relieve pain and improve range of motion and strength.
• Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) like Advil (ibuprofen) and Aleve (naproxen) can reduce inflammation and pain, but take them only as directed.
• Cortisone injections by a healthcare provider can temporarily reduce pain.
  

If you have injured your AC joint, follow your healthcare provider's advice, which may include the above treatment. You may also wear a sling temporarily to reduce movement. If your shoulder is dislocated, your provider can give you an anesthetic before they put the shoulder joint back into place (called reducing the dislocation).

Shoulder dislocations or separations don't usually require surgery unless ligaments need repair. Recovery depends on how severe the injury is. It can generally take anywhere from a couple of weeks to two months.

If the pain persists, your provider may recommend arthroscopy, which is a minimally invasive procedure to remove debris or tissue that may be causing pain. Shoulder replacement is an option for people with severe arthritis to relieve pain. Shoulder replacement requires rehabilitation and takes months to heal.

If you have fractured a bone, you may need surgery if there are bone fragments that need to be fixed in place, but about 80% of fractures don't require surgery.

Are There Fast Ways to Heal?

The most efficient way to heal an AC injury is to follow your healthcare provider's guidelines. Healing will take time, but rest followed by gentle exercise can help you build movement and strength in your shoulder.

Managing AC Joint Pain While Sleeping

You may be able to alleviate some AC joint pain while you sleep by changing your position so that there is less pressure on the affected shoulder. Avoid sleeping on the affected side and try a plump pillow under your arm to keep it elevated. Try keeping your shoulder back rather than tilted forward.

If you sleep on your back, tuck a small pillow under each arm or a foam wedge under your back so that your body is at a slight incline. You can also try a pillow or soft foam roller under your knees.

Summary

AC joint pain is very common but it can also disrupt your daily life. The pain may be from arthritis or from an injury, which can include shoulder dislocation. AC joint pain from arthritis tends to worsen, but there are treatments and possible shoulder replacement to alleviate the pain.

AC joint pain from an injury doesn't usually need surgery, but rest, ice, exercises, and pain medication as directed by a healthcare professional can help you heal.

A Word From Verywell

If shoulder pain is bothering you enough that it's waking you up or making you miserable during the day, there are ways to manage it. Take the time to address AC joint pain by seeing a healthcare provider so you'll know how you can best handle it and minimize the discomfort.