We use our shoulders for a wide range of movements. They allow us to raise, swing, bend, and rotate our arms. Thanks to them, we can throw a ball and scratch our noses. Our shoulders are the most flexible joint in our bodies and also the most complex. 

The flexibility of our shoulders does not come without issue — these remarkable structures are prone to injury. 

One of the most common shoulder injuries is an acromioclavicular (AC) joint separation, also called a shoulder separation. AC separations are particularly common in active individuals, especially athletes who play contact sports. 

AC Joint Anatomy

The AC joint is where the shoulder blade’s highest part (acromion of the scapula) meets the collarbone (clavicle). Muscles and ligaments surround and support the shoulder blade and collarbone. 

An AC separation is a tear in one or more of these supportive ligaments — the acromioclavicular (AC) or the coracoclavicular ligament (CC). The severity of an AC joint separation is graded according to whether both ligaments are injured and the degree to which they are damaged. 

AC separations are commonly caused by a fall onto the point of the shoulder or an outstretched arm (such as when tripping or going over a bike’s handlebars). Direct blows to the shoulder during sports like football or high-impact collisions like those in car accidents can also cause shoulder separations.

AC Joint Separation Symptoms

Common symptoms of shoulder separations are bruising, swelling, pain, and instability in the shoulder and arm. Symptoms generally last several days to a few months, depending on the severity of the injury. 

Pain is usually worse when lifting one’s arm overhead or trying to sleep on that side. In higher-grade injuries, the collarbone may also lose its alignment with the shoulder blade.

AC joint separations are diagnosed by a physical exam from an orthopedic shoulder specialist. Sometimes the specialist will inject an anesthetic into the area to relieve pain as they manipulate the injury. Not all shoulder separations are visible, so an X-ray may also be necessary.

AC Joint Separation Grading 

Shoulder separations are categorized by the degree to which the AC’s joints surrounding ligaments are stretched or torn. Injuries range from grade I to grade VI, with grade I being the most common. 

Tearing only the acromioclavicular ligament, a grade I or II injury, isn’t serious. In fact, most of these injuries heal on their own. If the coracoclavicular ligaments are ruptured (as in a grade III injury), however, healing can be more complicated since the whole shoulder is involved.

Grades IV-VI are quite uncommon and involve tearing additional muscles across the shoulder and neck.  

Grade I 

• Most common
• Acromioclavicular ligament is either stretched or slightly torn
• Bruising, swelling, tenderness, minor pain
• May have a slight displacement
• General healing timeline is several days to two weeks 
• Full release back to contact sports or activities requiring overhead motions can take longer

Grade II

• Acromioclavicular ligament is completely torn, but the coracoclavicular ligament remains intact
• Bruising, swelling, moderate to severe pain, pain when moving arm
• May have a small bump on top of the shoulder at the end of the collarbone
• Partial dislocation, but displacement may not be obvious
• General healing timeline is two to six weeks

Grade III

• Both ligaments are torn, as is the capsule surrounding the joint
• Bruising, swelling, pain, and possible popping noise with movement
• Displacement is usually obvious
• Shoulder may sag due to the weight of the arm, and the injured person often reflexively holds their arm close and supports their elbow
• Collarbone gets pushed up, causing a bump on the shoulder
• General healing timeline is six to 12 weeks

AC Joint Separation Treatment 

Treatment for a shoulder separation depends on the grade of the injury. Most treatment protocols include icing and resting the injury, wearing a supportive arm sling, and taking pain and anti-inflammatory meds as directed by your orthopedic shoulder specialist.

Pain management also includes avoiding reaching over your head, across your body, leaning on your elbows, and sleeping on the injured shoulder. As you heal, your specialist will introduce AC joint separation exercises to restore normal range of motion and strength. 

Good range of motion and pain-free function often return with proper care as recommended by your orthopedic shoulder specialist. 

AC Separation Surgery 

Even with a grade III separation, surgery is typically unnecessary. Surgery may be indicated if non-surgical treatments don’t work and the pain persists in the months following injury. Surgery may also be an option for young, active athletes or workers who need to lift their arms over their heads regularly. 

Grades IV-VI are the most severe types of AC separations and require immediate care from an orthopedic shoulder surgeon — surgery is likely necessary for these types of separations. 

Regardless of whether an AC joint separation is treated surgically, complications can occur. The most common issues are a feeling of instability when lifting one’s arm overhead and the development of arthritis in the joint. If a separated AC joint results in a visible bump, the bump may remain even after the injury has healed.

If you’ve injured your shoulder or are experiencing shoulder pain and would like to talk to one of our orthopedic shoulder specialists, please contact us or comment below. We would be more than happy to discuss the next steps with you.