The acromioclavicular (AC) joint is located just above the shoulder joint. The shoulder is made up of three bones: the scapula (shoulder blade), the humerus (upper arm bone), and the clavicle (collarbone). The part of the scapula that makes up the roof of the shoulder and connects with the clavicle is called the acromion. The joint where the acromion and the clavicle join is known as the AC joint.

At first treatment for AC joint injury is often rest and anti-inflammatory drugs such as aspirin or ibuprofen. A rehab program with a physical or occupational therapist may be needed. If the pain doesn't go away, an injection of cortisone into the joint may help. Cortisone is a drug that decreases inflammation and reduces pain. Cortisone's effects are only temporary. The short-term relief can be very helpful.

For the AC joint, injection may be used for diagnosis. If painful symptoms are relieved by the injection, the AC joint is the most likely cause. In making this decision, ask your doctor if the injection is to diagnose or to treat the problem?

Joint injection should be used after other more conservative treatment is tried. This may include nonsteroidal anti-inflammatory drugs, physical therapy, and changing activities.