The acromioclavicular (AC) joint unites the shoulder's cap (acromion), which is part of the shoulder blade and the collar bone (clavicle), holding them together with the help of the strong AC and coracoclavicular (CC) ligaments. Even though the joint is durable, its location leaves it vulnerable to injuries that can result in sprains or separations.
AC joint injuries are most frequent in individuals under 35, with males being 5 times more prone. Injuries can result from overuse and trauma, especially in the case of sports requiring repeated overhead motions or high-impact collisions:
AC joint injuries can also occur due to falling improperly on an outstretched arm during sports involving high velocities like skiing, ice skating, and cycling, or non-athletic causes like falling off a ladder. AC joint injuries can also be sustained due to overuse in non-athletic occupations such as construction work or from the gradual deterioration caused by aging.
When AC injuries occur and the symptoms are evident, some individuals may dismiss them as discomfort common with contact sports or a normal part of the aging process. Ignoring symptoms and leaving them untreated may worsen the injury and produce long-term consequences like arthritis, collarbone fracture or displacement, severe shoulder separation, and damage to adjacent structures like the rotator cuff.
Regardless of the injury's cause, AC joint injuries share similar symptoms:
Differential diagnosis is required to assess the damage and rule out other potential injuries like rotator cuff tears, arthritis, biceps tendonitis, or scapulothoracic bursitis. X-ray imaging and physical examination are usually sufficient to determine the extent of AC joint injuries, ranging from I to VI depending on severity.