- Joint
- Acromioclavicular (top of shoulder)
- Common mechanism
- Fall onto the point of the shoulder
- Classification
- Rockwood I–VI
- Most heal without
- Surgery (grades I, II, often III)
- Surgical reserved for
- Grades IV–VI, chronic AC arthritis
Where the AC joint is.
The acromioclavicular joint sits at the very top of the shoulder, where the lateral end of the collarbone (clavicle) meets a part of the shoulder blade called the acromion. It is a small, mobile joint, held together by two sets of ligaments: the acromioclavicular ligaments (which run directly across the joint) and the much stronger coracoclavicular ligaments (which run from the clavicle down to the coracoid process below).
Acute AC joint separation.
An AC joint separation occurs when one or both of these ligament sets are torn — usually after a fall onto the point of the shoulder (commonly in rugby, mountain biking, or a cycling crash). The injury is graded I to VI on the Rockwood classification:
- Grade I — sprain of the AC ligaments only. No deformity. Heals with sling and analgesia.
- Grade II — AC ligaments torn, coracoclavicular ligaments intact. Mild prominence of the clavicle. Heals non-operatively in most cases.
- Grade III — both sets of ligaments torn; obvious bump. Treated non-operatively in most patients, with surgery considered for high-demand overhead athletes or persistent symptoms.
- Grade IV — clavicle displaced posteriorly through the trapezius. Almost always operative.
- Grade V — gross superior displacement of the clavicle. Operative.
- Grade VI — clavicle displaced inferiorly (rare). Operative.
How the diagnosis is made.
Clinical examination identifies tenderness directly over the AC joint and a visible step or bump in higher-grade separations. The most sensitive provocation test is cross-body adduction. Plain radiographs in dedicated AC views confirm the diagnosis and grade the injury. MRI is obtained before consultation to assess the rotator cuff, labral integrity and associated pathology, so that Dr Coory has a complete picture on the day.
Non-operative treatment.
Most low-grade AC injuries (grades I, II and most III) are treated non-operatively:
- Sling immobilisation for 2–4 weeks for comfort.
- Analgesia and anti-inflammatories.
- Physiotherapy beginning with passive range of motion, progressing to scapular control and strengthening.
- Return to non-contact activity in 4–6 weeks; return to contact sport in 8–12 weeks.
When surgery is considered.
Surgery is recommended for:
- High-grade separations (Rockwood IV–VI) acutely.
- Persistent symptoms after a grade III separation in a high-demand overhead athlete.
- Chronic AC instability with ongoing pain and dysfunction.
The operation is AC joint reconstruction — typically using a combination of suture-button suspension between clavicle and coracoid, plus a biological graft to restore the coracoclavicular ligaments.
AC joint arthritis & distal clavicle osteolysis.
The AC joint also develops osteoarthritis over years, particularly in patients with a history of trauma to the joint, or in heavy lifters and bench-pressers (the latter often shows up as distal clavicle osteolysis). The pain is localised to the top of the shoulder, worse with cross-body adduction, and reliably reproduced on examination. Non-operative treatment includes activity modification, anti-inflammatories, and a well-placed image-guided corticosteroid injection. When these fail, arthroscopic distal clavicle excision (the Mumford procedure) is a reliable and durable operation.
Frequently asked questions.
Will the bump from my AC separation go away?
A residual bump is common in grade II or III separations and does not necessarily indicate a failed recovery. Pain and function matter more than appearance.
Can I return to contact sport after a grade III?
Most patients return to contact sport after a grade III separation managed non-operatively, at around 8–12 weeks. Surgical reconstruction is considered when symptoms persist beyond a normal rehabilitation period.
Is bench-pressing painful for me because of my AC joint?
Pain at the top of the shoulder with bench press, push-ups or dips is a classic feature of AC joint pathology — either chronic arthritis or distal clavicle osteolysis. The diagnosis is clinical and confirmed on imaging.
Will a cortisone injection help my AC joint?
Yes — image-guided AC joint injection is a high-yield diagnostic and therapeutic test. Long-term relief varies; the response is also useful in deciding whether distal clavicle excision will help.
How long is the recovery from AC joint reconstruction?
Sling for 3 weeks. Return to driving at approximately 3 weeks. Return to non-contact sport at 3 months. Return to contact sport at 4–6 months.
References.
- Rockwood CA Jr. Injuries to the acromioclavicular joint. In: Rockwood and Green's Fractures in Adults. 5th ed. Lippincott; 2001.
- Beitzel K, et al. Current concepts in the treatment of acromioclavicular joint dislocations. Arthroscopy. 2013;29(2):387–397.
- Mall NA, et al. Acromioclavicular joint reconstruction. J Am Acad Orthop Surg. 2013;21(5):295–305.