The acromioclavicular (AC) joint is a small joint at the top of the shoulder where the collarbone (clavicle) meets the acromion (part of the shoulder blade).
AC joint injuries are common after falls, sporting impacts, and other direct trauma to the shoulder. They can cause pain on the top of the shoulder, difficulty lifting the arm, and discomfort when lying on the affected side. The AC joint equally commonly becomes painful and inflamed without a single injury, but through overload such as regular weights training, or through degenerative changes as we age. AC joint injuries range from mild sprains to complete separations, and the most appropriate treatment depends on the severity of the injury, your activity level, and how symptoms affect daily life.
The AC joint sits at the outer end of the collarbone and forms part of the shoulder’s overall structure. While it is small, it plays an important role in:
The joint is stabilised by several ligaments, including:
Damage to these ligaments is what determines the severity of an AC joint injury.
AC joint sprain: A mild injury where the ligaments are stretched but not completely torn. The joint remains stable, though pain and swelling may occur. The internal cartilage disc may be damaged, and the internal lining is inflamed.
AC joint separation: A more significant injury where the ligaments are torn and the collarbone can shift out of position. This is often referred to as a “separated shoulder.”
Note: A separated shoulder – referring to AC joint injury – is different from a shoulder dislocation, which involves the ball-and-socket joint.
AC joint arthritis (wear and tear): Some people experience AC joint pain due to arthritis rather than acute injury. Arthritis often causes pain with reaching across the body or lifting. It can be due to overload through work or sport, or simply occur as people age.
This page focuses primarily on acute AC joint injuries, though arthritis may be discussed if it contributes to pain.
Symptoms may range from mild discomfort to significant pain and functional limitation depending on injury severity.
AC joint separations are often described using a grading system based on ligament damage and displacement.
In simple terms:
AC joint clean up (debridement)
In cases where AC joint pain is driven by inflammation/arthritis rather than separation, arthroscopic debridement including removal of a small portion of the end of the collarbone may be considered.
This is generally reserved for persistent symptoms after non-operative care
Dr Dallalana will explain the appropriate options based on injury type and imaging.
Specialist assessment and individualised care
AC joint injuries can vary significantly in severity, symptoms, and functional impact, and management is not one-size-fits-all.
Dr Richard Dallalana provides specialist assessment of AC joint injuries and shoulder trauma, with a focus on:
Early specialist opinion is valuable in the case of high grade injury with visible deformity to determine the need for surgery. Delayed surgery is more complicated, usually requiring a ligament reconstruction rather than a smaller procedure enabling the existing torn ligaments to heal.
A thorough shoulder assessment can help confirm the diagnosis, grade the injury, and guide the most appropriate management plan.
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