AC Joint Separation (Shoulder Separation)

What the AC joint is

The acromioclavicular (AC) joint sits at the top of the shoulder where the outer end of the collarbone (clavicle) meets the acromion, a bony part of the shoulder blade. Two sets of ligaments hold it steady:

• AC ligaments: wrap around the joint itself
• Coracoclavicular (CC) ligaments: strong bands that anchor the collarbone downward to the shoulder blade

A shoulder separation is different from a shoulder dislocation. In a dislocation the ball of the upper arm comes out of the socket. In a separation the collarbone and shoulder blade are pulled apart.

Causes

• A direct fall onto the point of the shoulder with the arm at the side, which drives the acromion down while the collarbone stays put
• Contact sports such as football, rugby and hockey
• Cycling and mountain biking falls
• Skiing, snowboarding, wrestling and martial arts
• Less often, a fall on an outstretched hand

Young men in contact sports are the most commonly affected.

Symptoms

• pain on top of the shoulder, at the outer end of the collarbone
• swelling and bruising
• a bump at the top of the shoulder, more visible in higher grades
• pain when lifting the arm, reaching across the body or lying on that side
• reduced shoulder movement in the first days
• occasionally a popping or clicking sensation

Grades of AC joint separation

Diagnosis

A doctor will ask how you fell, examine the shoulder for a step or bump, press over the AC joint, and test movement, strength and the nerves and circulation of the arm. The cross-body adduction test, bringing the arm across the chest, typically causes pain at the AC joint.

• X-rays of both shoulders confirm the injury, show its grade, and rule out a collarbone fracture
• Special X-ray views show backward displacement in grade 4 injuries
• MRI is used if a rotator cuff injury or other damage is suspected

Treatment

Non-surgical treatment (grades 1 to 3)

• Sling for comfort: a few days for grade 1, up to 1 to 3 weeks for grades 2 and 3
• Ice for 15 to 20 minutes several times a day for the first 2 to 3 days
• Pain relief: acetaminophen (paracetamol) or ibuprofen at the label dose, avoiding NSAIDs if you have kidney disease, stomach ulcers or take blood thinners
• Physical therapy: gentle range-of-motion exercises as soon as pain allows, then strengthening of the rotator cuff and shoulder blade muscles
• Gradual return to sport once you have full, pain-free movement and normal strength. Padding can protect the joint in contact sports

Surgery

Surgery is recommended for grades 4, 5 and 6, and considered for some grade 3 injuries in throwing athletes, people who do heavy overhead work, or those who still have pain and weakness after 3 months of rehabilitation. Procedures reconstruct the CC ligaments, often using a tendon graft or a strong suture device, and hold the collarbone in place while they heal. After surgery a sling is worn for about 4 to 6 weeks, with physical therapy for several months.

Recovery time

Will the bump go away?

In grade 2 and higher injuries, the bump usually stays because the torn ligaments heal in a lengthened position. For most people it is only cosmetic and does not affect strength or function. A minority have ongoing pain, clicking or fatigue with overhead work.

Complications

• persistent pain or instability at the joint
• AC joint arthritis years later, causing pain with overhead lifting and reaching across the body
• osteolysis: thinning of the end of the collarbone, especially in weightlifters
• stiffness if the shoulder is kept immobilized for too long

Long-term AC joint arthritis can be treated with injections or surgery to remove a small piece of the end of the collarbone.

Frequently asked questions

How long does an AC joint separation take to heal?

Grade 1 injuries usually recover within 1 to 2 weeks and grade 2 within 2 to 6 weeks. Grade 3 injuries treated without surgery typically take 6 to 12 weeks. After surgery for higher grades, return to full contact sport often takes 3 to 6 months.

Does a separated shoulder need surgery?

Most do not. Grades 1 and 2, and most grade 3 injuries, heal well with a sling, physical therapy and time. Surgery is usually recommended for grades 4 to 6, and is considered for grade 3 injuries in overhead athletes or people with ongoing pain and weakness.

Is a separated shoulder the same as a dislocated shoulder?

No. In a separated shoulder, the ligaments between the collarbone and shoulder blade are injured at the top of the shoulder. In a dislocated shoulder, the ball of the upper arm bone comes out of the shoulder socket. They are treated differently.

Will the bump from a shoulder separation go away?

Usually not completely in grade 2 and higher injuries, because the ligaments heal longer than before. The bump is mostly cosmetic. Most people regain normal strength and movement even though the bump remains.

Can I play sports with an AC joint separation?

You can return once you have full, pain-free movement and normal strength, which your physical therapist will check. That may be within a couple of weeks for a grade 1 injury and several months after surgery. Shoulder padding helps protect the joint in contact sports.