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AC Joint Injuries


The AC joint (acromioclavicular joint) is a joint at the top of the shoulder. There are three bones that form the shoulder joint: the collarbone (clavicle), the shoulder blade (scapula) and the arm bone (humerus). The socket of the shoulder joint is formed by the shoulder blade and collarbone. The acromion is the end of the shoulder blade, and the joint between the acromion and the clavicle is called the acromio-claviculat (AC) joint. The AC joint is the most protruding bony process on the upper part of the collarbone.

The AC joint allows you to raise your arm above your head. It acts as a pivot point to increase your range of motion.

Common AC Joint Injuries & Symptoms

AC Arthritis

AC Arthritis occurs when the AC joint wears thin due to repeated movements wearing the cartilage surface down. Symptoms of AC arthritis can take a while to emerge, but eventually patients complain of pain associated with certain shoulder movements.

AC Joint Separation

Also referred to as shoulder separation injury, AC joint separation is one of the most common AC joint injuries often caused from a specific event that involved a traumatic blow to the top of your shoulder or a fall onto an outstretched hand. A direct blow to your shoulder is most commonly seen in impact sports like football, hockey or rugby and falling on to an outstretched hand usually occurs when falling off a horse, motorcycle, and bicycle or from an elevated platform. The most common symptom of AC joint separation is severe pain and numbness. The pain occurs nearly immediately upon separation and swelling occurs shortly after.

Call (310) 595-1030 to schedule a consultation with Dr. Millstein if you have an AC joint injury.

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