Overview
The acromioclavicular (AC) joint is the small joint at the top of the shoulder where the outer end of the collarbone meets the acromion of the shoulder blade. Two sets of ligaments hold it: the AC ligaments around the joint, which control front-to-back movement, and the coracoclavicular ligaments underneath, which stop the collarbone riding upward. A “separation” is a sprain or rupture of those ligaments, graded I through VI by which ligaments are torn and how far the collarbone has displaced.
The grade determines most of the treatment. Grade I and II injuries keep their coracoclavicular ligaments and heal without surgery. Grade IV, V and VI injuries are reconstructed. Grade III, where the collarbone sits a full width above the acromion, is the one that requires a real discussion, and the answer depends on the patient's sport, occupation and dominant arm as much as on the X-ray.
Common Symptoms
- Sharp pain and tenderness directly over the top of the shoulder, at the end of the collarbone
- A visible bump where the collarbone sits higher than the acromion; in higher grades the skin over it is stretched
- Pain reaching across the body, lying on the injured side, or lowering into a push-up or bench press
- In chronic cases, clicking with overhead motion and a joint that feels loose front-to-back
Tenderness at the very end of the collarbone separates an AC injury from its neighbors. Pain and deformity further in along the bone is a clavicle fracture, which follows the same fall. Weakness lifting the arm after a hard landing raises the question of a rotator cuff tear, and a shoulder that felt as if it came out of the socket points to shoulder instability.
Causes & Risk Factors
The mechanism is nearly always a direct fall onto the point of the shoulder with the arm at the side, driving the acromion downward while the collarbone stays put. Cyclists going over the handlebars, skiers and snowboarders catching an edge, and hockey and football players taking a tackle account for most AC injuries. Young adult men are affected most; the same fall in a patient over 50 is more likely to fracture the distal collarbone or tear the cuff than to separate the joint.
How It Is Diagnosed
Dr. O'Donnell palpates the joint line, checks whether the collarbone can be pushed back into place and held there, tests front-to-back stability of the collarbone, and performs the cross-body adduction test, which compresses the joint and reproduces the pain. He also examines the rotator cuff, since the same fall can injure more than one structure.
X-rays confirm the grade. A Zanca view, angled slightly upward, shows the joint clearly and lets the distance between the coracoid and the collarbone be measured against the uninjured side; an axillary view shows whether the collarbone has been pushed backward, which distinguishes a grade IV from a grade III. MRI is ordered when the exam suggests an associated cuff or labral injury, or in chronic cases before reconstruction. Out-of-town patients can upload existing images through mymedicalimages.com for review before traveling.
Treatment Options
Non-operative care
Grade I and II separations, and most grade III injuries, are treated without surgery. The arm rests in a sling for one to three weeks for comfort, then motion is restored and the rotator cuff and shoulder-blade muscles are strengthened so the shoulder blade is held up against the collarbone by muscle rather than by torn ligament. Most grade I and II patients are back to full activity in two to six weeks; grade III usually takes six to twelve. The bump does not go away, but the shoulder works. A joint still sore months later usually settles with an ultrasound-guided corticosteroid injection.
AC joint reconstruction
Dr. O'Donnell recommends AC joint reconstruction for grade IV, V and VI injuries, and for grade III injuries in overhead athletes, heavy manual workers, and patients whose dominant shoulder remains painful or weak after a proper course of rehabilitation. The operation rebuilds the coracoclavicular ligaments so the collarbone sits where it belongs. Timing changes the technique: within about three weeks of injury the native ligaments can be stabilized directly, while a chronic separation needs a tendon graft to replace ligament that has scarred in the wrong place. The procedure is performed as an outpatient at Bayside Surgery Center.
Recovery & What to Expect
After reconstruction the weight of the arm pulls on the repair, so the sling is worn longer than after most shoulder operations and loaded activity is delayed until the graft has healed.
| Phase | Timing | What happens |
|---|---|---|
| Maximum protection | Weeks 0–6 | Sling at all times, arm supported when upright. Pendulums and passive motion to 90° only; no active elevation, no lifting, pushing or leaning through the arm. |
| Motion | Weeks 6–12 | Sling discontinued at about 6 weeks. Active-assisted then active motion to full overhead; light scapular and cuff strengthening. No heavy lifting. |
| Strengthening | Weeks 12–16 | Progressive cuff, deltoid and periscapular resistance; overhead and pressing loads begin after 12 weeks. Advance at 80% strength of the other side. |
| Return to activity | Months 4–6 | Plyometrics and sport- or job-specific progression. Contact and collision sport typically at 5 to 6 months. |
Desk work is usually possible within a week with the arm in the sling, driving once the sling is off at about 6 weeks, and road cycling, skiing and contact sport at 5 to 6 months. The full protocol is available as a PDF: AC Joint Reconstruction rehabilitation protocol.
Frequently Asked Questions
Can an AC joint separation heal on its own?
Grade I and II injuries heal fully because the main supporting ligaments are intact. In a grade III the coracoclavicular ligaments are torn and do not regrow, but the shoulder-blade muscles take over well enough that most patients regain a strong, painless shoulder without surgery. Grades IV to VI do not recover usefully on their own and are reconstructed.
Will the bump on my shoulder go away?
No. Once the collarbone has displaced above the acromion it stays there unless the joint is reconstructed. For most patients the bump is cosmetic only. It becomes a reason for surgery when it comes with persistent pain, weakness with overhead work, or skin stretched thin over it.
Do I need surgery for a grade 3 AC separation?
Usually not. Dr. O'Donnell treats most grade III injuries with a sling and rehabilitation first and reserves reconstruction for overhead athletes, heavy manual workers, and patients whose shoulder is still painful or weak after 6 to 12 weeks of rehabilitation. If surgery is likely, it is technically easier within the first 3 weeks.
How long will I wear a sling after AC joint reconstruction?
Six weeks, longer than after most shoulder procedures. The reconstruction has to resist the downward pull of the arm while it heals, so the sling carries that weight. Passive motion within 90 degrees begins in the first days to keep the shoulder from stiffening, and the sling comes off at about 6 weeks.
When can I do push-ups or bench press again?
After non-operative treatment of a grade I or II injury, once the joint is no longer tender, usually 3 to 6 weeks. After reconstruction, pressing loads begin after 12 weeks and heavy bench press waits until strength is symmetric, typically 4 to 6 months.
How soon can I be seen after a cycling or skiing crash?
Same-week appointments are kept for acute injuries; call (305) 393-8810. An X-ray at the first visit grades the injury and sets the plan, and a grade that needs surgery is easier to fix in the first 3 weeks. Visiting athletes can upload images through mymedicalimages.com before they arrive.
This page is for general education and is not a substitute for a medical evaluation. Treatment recommendations depend on your individual diagnosis and goals. Kevin O'Donnell, MD sees patients from Coral Gables, Miami, Brickell, Pinecrest and Coconut Grove at 475 Biltmore Way, and out-of-town patients by telemedicine.