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AC Joint Pain

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. 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. Advanced AC joint injuries can cause lost time at work. Leaving an AC joint injury untreated means your condition can worsen, which can have serious consequences, such as severe shoulder separation, serious displacement, or a collarbone fracture. It can cause damage to nearby joints such as the rotator cuff. Instead of waiting until it gets to that point, if you are experiencing any debilitating symptoms, you should see one of the first-class orthopedic specialists at OCC – Advanced Orthopedic & Sports Medicine Specialists in Denver, Parker, or Aurora, Colorado. 


inflammation is the body’s natural response to injury, disease, overuse, or degeneration, and it often causes swelling, pain, or irritation. Inflammation of the AC or acromioclavicular joint is a frequent cause of pain in the top portion of the shoulder and is usually caused by arthritis or an injury. Acromioclavicular joint injuries account for more than forty percent of all shoulder injuries. An acromioclavicular joint injury can result in a severe AC sprain, AC fracture, or an AC joint separation, which occurs when the collarbone (clavicle) separates from the shoulder blade (acromion). Shoulder injuries involving the AC joint are more common among males than females. Males in their 20s and 30s are more likely to experience these injuries.


The shoulder is a complex, ball-and-socket joint made up of three bones: the upper arm bone (humerus), shoulder blade (scapula), and collarbone (clavicle). The ball, or head, of the upper arm bone fits into a rounded socket (glenoid) in the shoulder blade. The arm bone is kept centered in the shoulder socket by a combination of muscles and tendons (rotator cuff). The rotator cuff covers the head of the upper arm bone and attaches it to the shoulder blade. The AC joint is where the acromion (the tip of your shoulder blade—scapula) meets your clavicle(collarbone). Cartilage (flexible but tough tissue) forms a cushion between these bones. A thin layer of synovial fluid also helps lubricate the joint. This joint helps maintain the position of the shoulder and is very important for shoulder control, motion, and strength. The joint is stabilized by a capsule and ligaments, and injury occurs when these structures are damaged. When the capsule and ligaments are injured, the joint can become unstable and painful, and shoulder function can be affected. 


AC joint pain can be caused by various factors, including arthritis, injuries, repetitive overuse, or degenerative changes.


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


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. Two ligaments may be involved–the AC ligament and the coracoclavicular (CC) ligament AC joint injuries range from minor to incapacitating and are divided into three categories by degree of severity as follows:

Type 1: ligaments surrounding the AC joint have been stretched or sprained but not torn.

Type 2: The AC ligament is torn, and there is minor damage to the CC ligament, but it isn’t torn.

Type 3: both ligaments are torn so that the collarbone is separated from the shoulder blade. AC joint injuries can occur in any athletic activity where falling or hard contact with an opponent is possible. This contact can suddenly push the shoulder blade away from the collarbone, stretching or tearing the ligaments that support the AC joint. The most common sports that see AC joint injuries include football, cycling, mountain biking, martial arts, lacrosse, skiing, snowboarding, and hockey. 

Repetitive Overuse

Most common in individuals who perform tasks such as heavy weight lifting (bench and military presses) or those with jobs that require physical labor with arms stretched over the head like construction. Even tasks that involve lifting arms overhead such as painting ceilings can lead to injury. Activities that involve frequent reaching across the body such as in tennis or baseball can strain the AC joint.

Degenerative changes

With age, osteoarthritis—also known as “wear and tear” arthritis can destroy the articular cartilage (smooth outer covering of bone in the AC joint,  resulting in inflammation. As the cartilage wears away and becomes frayed and rough, the protective space between the bones decreases. During movement, the bones of the joint rub against each other and cause pain. Osteoarthritis usually affects people over 50 years of age.

Other causes include prolonged computer use without proper ergonomic setup, regularly carrying heavy bags or backpacks on one shoulder, and poor posture.

Read more about AC Joint Pain on our new Orthopedic News Site – Colorado Orthopedic News. Schedule an appointment with a shoulder specialist today.

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