Acromioclavicular (AC) Joint Injury

An AC joint injury is a shoulder injury involving the ligaments that hold the acromion and the clavicle (collarbone) together. That’s where the name acromioclavicular or AC injury comes from.
The acromioclavicular joint is the highest point of the shoulder.

Description: Acromioclavicular (AC) Joint Injury

The function of the AC joint is to help raise the arm above head level.
There are four ligaments that attach the clavicle (collarbone) to the rest of the shoulder:

Acromioclavicular ligament – the direct junction between the acromion and clavicle.
Coracoacromial ligament – connects the coracoid process to the acromion.
Coracoclavicular ligaments – include the conoid and trapezoid ligaments (see illustration above).

In an AC joint injury, one or more of these ligaments may become injured, inflamed, or torn.
Common AC joint injuries include dislocations (also called AC joint separations or shoulder separations).
However, be careful not to confuse an AC dislocation with a shoulder dislocation:

A shoulder dislocation occurs when the upper arm bone (humerus) pops out of its socket.
An AC dislocation happens when the acromion separates from the clavicle.

Grading of AC Dislocations

Grade 1: The acromioclavicular ligament is partially torn. The gap between the acromion and clavicle is less than 4 mm.
Grade 2: Complete dislocation of the AC ligament with partial disruption of the coracoclavicular ligaments. The gap between the acromion and clavicle is greater than 5 mm.
Grade 3: Severe injury. Both the AC and coracoclavicular ligaments are completely disrupted.

Symptoms: Acromioclavicular (AC) Joint Injury

Pain at the outer end of the collarbone, especially when raising the arm above head level.
Swelling.
Visible deformity, especially in Grade 2 and Grade 3 injuries.

Who Is Susceptible: Acromioclavicular (AC) Joint Injury

Wrestlers
American football players
Ice hockey players

Treatment: Acromioclavicular (AC) Joint Injury

Rest and apply ice as soon as possible.
Use an arm sling to reduce stress on the shoulder.
Consult your doctor, who may:
- Tape your shoulder joint into the correct position.
- Prescribe an anti-inflammatory medication to reduce pain and swelling.
- Recommend a rehabilitation program.
- Perform surgery if necessary.

Advice: Acromioclavicular (AC) Joint Injury

Strengthen your shoulders regularly.
Do not attempt wrestling, judo, or aikido throws without the supervision of an experienced coach.
Warm up and stretch your upper body before training.
Rest, apply ice, and see a sports injury specialist as soon as possible.