Shoulder AC Separation | Everything You Need to Know

Written by on October 29, 2021 — Medically reviewed by John Doe

Xray of shoulder AC separation

Imagine running on a football field, meters away from the goal to win the game, only to get tackled from behind. You try to brush it off but you notice a searing pain and a noticeable bump on your shoulder. These can be signs of shoulder AC separation.

To get you up to speed on this injury, we’ll talk about:

  • What causes a separated shoulder
  • Separated shoulder symptoms
  • Best treatment options for each type
  • Other questions you may have about AC joint separations

But, to give you some context, let’s start with the AC joint.

What is the AC joint?

The acromioclavicular (AC) joint is where your collarbone meets your shoulder blade. It’s a stable joint thanks to ligaments and muscles that keep it in place.

These include:

  • Acromioclavicular ligament
  • Coracoclavicular ligament
  • Deltoid Muscle
  • Trapezius Muscle
  • Joint Capsule

As part of the shoulder joint, its main functions are:

  • To add a range of motion to the shoulder blades whenever we move our arm, and
  • Allow transmission of force from your arm to your trunk

What is an AC joint separation? 

AC Joint separation is synonymous with shoulder separation. It happens when the ends of your collarbone and shoulder blade get disconnected.

Shoulder separation accounts for about 12% of all shoulder injuries. Moreover, 50% come from athletes who take part in contact sports. (1)

What causes a separated shoulder?

A separated shoulder is the result of a direct blow to your ac joint. This acute trauma can lead to a sprain or disruption of the soft tissues surrounding your AC joint.

Common examples of these traumas include (2):

  • Falling on the outer part of your shoulder
  • Violent hit directly on the joint
  • Falling on an extended arm

Who is at risk?

According to research from Emergency Medicine International, people at risk are usually (3):

  • Male
  • People between 20-39 years of age
  • Those who take part in contact sports

Examples of sports with a higher tendency of causing AC joint injuries include (1):

  • Football
  • Soccer
  • Hockey
  • Rugby
  • Skiing

Other traumatic mechanisms can include road accidents, accidental falls, and work-related injuries. (3)

Types of AC joint separation

The Rockwood Classification is the most common way of rating the severity of your injury.

Here, there are 6 types of AC joint separation, depending on what soft tissues were damaged. (4)

For your reference:

  • AC = Acromioclavicular
  • CC = Coracoclavicular

Type I

  • Sprain of the AC ligament

Type II

  • Tear of the AC ligament 
  • Mild shoulder separation

Type III

  • Torn AC and CC ligaments
  • 25% to 100% displacement of the collarbone relative to the uninjured shoulder.
  • This is the most common type of acromioclavicular joint separation. (3)

Type IV

  • Torn AC and CC ligaments 
  • The collarbone is displaced into the trapezius fascia.

Type V

  • The AC and CC ligaments, as well as the origin of the deltoid and insertion of the trapezius, are torn. 
  • The CC distance is increased from 100% to 300%. This can cause extreme instability to the AC joint.

Type VI

  • The end of the collarbone is displaced into the subcoracoid position.
  • Most severe shoulder separation

What does it feel like?

Possible signs and symptoms of a separated AC joint include (5):

  • Bruising or skin discoloration on the shoulder joint and collar bone
  • Difficulty sleeping on the affected shoulder
  • Intense shoulder pain right after a fall or direct blow
  • Limited shoulder movement
  • Pain relief when crossing your affected shoulder towards your body
  • Radiating pain to the neck or arm during arm movement
  • Swelling on the tip of the shoulder blades
  • Tenderness on the collarbone or tip of the shoulder blade

Diagnosing a separated shoulder

It starts with your doctor doing a physical exam.

First, he/she will check for any bumps, bruises, and swelling in and around your AC joint.

A small bump on your AC joint can be a sign that your collarbone has separated from your shoulder blade.

Your doctor will also check the following during your physical exam:

  • Any clicking/grating noise on your shoulder
  • If you have a limited range of motion

These are often present with severe injuries associated with a shoulder separation.

Finally, your doctor will order imaging tests.

  • X-ray – This goes hand-in-hand with a physical exam. This checks your soft tissues’ structural integrity and rules out possible fractures.
  • Ultrasound and/or MRI – AC injuries can also come with a partially torn rotator cuff. These tests help your doctor check.

How is shoulder separation treated?

The “best” treatment depends on your symptoms and the classification of your shoulder joint separation.

But, generally speaking:

  • Types I and II respond well to non-operative treatment.
  • Types IV, V, and VI work best with surgery and rehabilitation. It’s the best option here because there is a proper fixation of the separated joint. (6)
  • Treatment for a type III injury will depend on your previous level of function. If you’re an athlete or someone who places a high demand on his/her shoulder girdle, surgery might be better. Otherwise, non-operative treatment should work just fine. (7)

Non-operative treatment for ac joint separation

The initial treatment includes a brief period of immobilization.

Here, your shoulder will be in a protective sling.

The sling supports the weight of your arm. It also helps limit the stress on your ligaments.

While on a sling, you can apply ice and take oral pain medications.

This conservative treatment helps calm down the pain and swelling.

A few words of caution, though:

Finally, go to physical therapy.

The primary goal here is for you to safely recover your range of motion and strength.

You can return to your previous activities once they’re back to normal and your symptoms are gone.

Surgical treatment for ac joint separation

If you’re on the higher end of the Rockwood Classification, surgery is going to be very likely.

As you might have guessed, higher classifications are also more severe. And, in turn, take more time to heal.

But, research says that shoulder injuries lose their healing potential after 3 weeks. Hence, the need for surgical correction. (8)

Some of the most commonly done surgical procedures include:

  • Stabilization with metallic devices – These fixate the dislocated joint and fractured collarbone. Examples are K-Wire, Bosworth Screws, and Hook Plate.
  • Suspensory device – This is a minimally invasive technique. It leaves off the hardware to provide extra stability to the joint.
  • Ligament and tendon reconstruction – The surgeon operates on the completely torn soft tissues. They can replace them with a graft taken from a donor or another part of your body.

What to expect after surgery

Rehabilitation will depend on the type of surgery done to you and the experience of your physical therapist.

But, generally, we PTs aim for (9):

  • Pain and swelling reduction
  • Restoration of scapular control
  • Increased range of motion
  • Increased strength and muscle recruitment
  • Sport-specific exercises if you’re an athlete

Recovering from AC separation

A non-operative course of treatment could last for 4-6 weeks or once your pain and swelling settle.

Non-contact sports can resume after 3 months of rehab. But, it will take about 6 months before you can take part in unrestricted sports activities. (10)


What is the difference between shoulder separation and dislocation?

Although separation and dislocation can mean the same thing, they describe two different joints in the shoulder.

 Shoulder separation involves the AC joint whereas a shoulder dislocation affects the glenohumeral joint.

Will the bump from AC separation go away?

This bump, also known as “step deformity”, indicates the separation between your collarbone and shoulder blade. Realigning your AC joint thru surgery fixes this cosmetic issue.

If left untreated, your torn ligaments may adapt to this position once it heals. You can still function with a shoulder deformity on the top of the shoulder.

Can you function with a separated shoulder?

Yes, you can still function with a separated shoulder. But, it can put a limit on how much stress your shoulders can handle.

Untreated, your injury can get worse and lead to complications, including chronic instability and abnormal scapular movement just to name a few. These can be avoided if you get your injury checked and treated right away.


Cuts, bruises, and injuries are common in sports and life. But something as traumatic as a shoulder separation injury can make you doubtful to return to previous activities. With the know-how to deal with this condition, we hope that it brings you guidance on your road to recovery.


  1. Warth, Ryan J et al. “Acromioclavicular joint separations.” Current reviews in musculoskeletal medicine vol. 6,1 (2013): 71-8. doi: 10.1007/s12178-012-9144-9
  2. Martetschläger, Frank et al. “The Diagnosis and Treatment of Acute Dislocation of the Acromioclavicular Joint.” Deutsches Arzteblatt international vol. 116,6 (2019): 89-95. doi: 10.3238/arztebl.2019.0089
  3. Chillemi, Claudio et al. “Epidemiology of isolated acromioclavicular joint dislocation.” Emergency medicine international vol. 2013 (2013): 171609. doi: 10.1155/2013/171609
  4. Gorbaty, Jacob D et al. “Classifications in Brief: Rockwood Classification of Acromioclavicular Joint Separations.” Clinical orthopaedics and related research vol. 475,1 (2017): 283-287. doi: 10.1007/s11999-016-5079-6
  5. Kiel J, Kaiser K. Acromioclavicular Joint Injury. [Updated 2021 Jul 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
  6. Allemann, F., Halvachizadeh, S., Waldburger, M. et al. Different treatment strategies for acromioclavicular dislocation injuries: a nationwide survey on open/minimally invasive and arthroscopic concepts. Eur J Med Res 24, 18 (2019).
  7. Li, Xinning et al. “Management of acromioclavicular joint injuries.” The Journal of bone and joint surgery. American volume vol. 96,1 (2014): 73-84. DOI: 10.2106/JBJS.L.00734
  8. Nolte, Philip C et al. “Optimal Management of Acromioclavicular Dislocation: Current Perspectives.” Orthopedic research and reviews vol. 12 27-44. 5 Mar. 2020, doi: 10.2147/ORR.S218991
  9. LeVasseur, Matthew R et al. “Acromioclavicular Joint Injuries: Effective Rehabilitation.” Open access journal of sports medicine vol. 12 73-85. 28 May. 2021, doi: 10.2147/OAJSM.S244283
  10. van Bergen, Christiaan J A et al. “New insights in the treatment of acromioclavicular separation.” World journal of orthopedics vol. 8,12 861-873. 18 Dec. 2017, doi: 10.5312/wjo.v8.i12.861