The acromioclavicular (AC) joint is located at the top of the shoulder where the collarbone and shoulder blade come together. It is a small but very important joint, promoting shoulder flexibility and arm strength. AC joint pain may occur acutely when the shoulder suffers physical trauma from a fall or sudden impact, or develop gradually over time due to arthritis or repeated minor injuries. AC joint pain may be accompanied by stiffness, weakness, and swelling, and it can significantly limit a person's ability to engage in everyday activities. Depending on the nature and severity of the problem, treatment may include a combination of rest, medications, physical therapy, and surgery.
AC joint injuries are fairly common among athletes, especially for those who play high-impact sports such as football. Chronic conditions such as arthritis may erode the cartilage in the AC joint over time, leading to a slow but progressive onset of symptoms. People who regularly lift weights or perform intensive manual labor are at risk of developing chronic AC joint pain as well. Osteoarthritis among older adults can also lead to shoulder joint problems.
A hard fall directly on the shoulder can cause immediate AC joint pain and swelling. In some cases, the joint may dislocate completely and cause the shoulder blade to protrude upward. It may be difficult or impossible to move the affected arm following an acute injury. In the case of chronic AC joint pain, a person may notice weakness and stiffness that are worst immediately following activities or when waking up in the morning.
Doctors can usually diagnose either type of AC joint injury by performing physical exams and taking x-rays. A physician might ask about lifestyle activities, medical history, and whether or not a major trauma recently occurred. Imaging scans may reveal eroded cartilage in the joint and damage to tendon or bone tissue.
Most cases of acute AC joint pain can be relieved with a period of rest, icing the joint, and taking anti-inflammatory drugs. A doctor might inject the joint with a corticosteroid if pain is unbearable. Chronic conditions may respond to the same types of treatments, in combination with arthritis drugs. Surgery is only needed if tendons are torn or if enough cartilage has worn away that the bones are rubbing against one another. An arthroscopic procedure can be performed to repair tissue and reinforce the joint with metal pins.
Patients who require surgery generally need to wait at least two months before returning to activity. Physical therapy sessions may be scheduled to help people build up strength and flexibility. Most patients who follow their rehabilitation schedules and their doctors' instructions are able to make full recoveries in about six months.