What is Acromioclavicular Joint Injury?

Acromioclavicular joint injury is a very common injury problem that affects men more than women. The highest incidence rate of this injury is found in the ages ranging from the 20s to the 30s. It is five times more likely to happen to men involved in sports like football, hockey, biking where chances of collision are high.

It is characterized by damage to the acromioclavicular joint and the structures surrounding it.

Around 40% of the shoulder-related injuries consist of the acromioclavicular joint. 

What is Acromioclavicular Joint Injury?

There are four ligaments (acromioclavicular ligaments and coracoclavicular ligaments) that hold the two bones of the acromioclavicular joint together. When an injury occurs to this joint, the ligaments are stressed causing separation in the joint. 

Two types of injuries can happen to the acromioclavicular joint: traumatic and overuse injuries. 

In traumatic acromioclavicular joint injury, damage happens to the ligaments holding the two bones together. This is injury is called a shoulder separation. These injuries are a result of a fall sustained by the shoulder. Depending on the separation of the joint, the injuries can vary from mild to severe. 

In overuse acromioclavicular joint injury, damage happens over some time. Repeated excessive stress being placed on the joint can cause this injury. The cartilage present at the end of the acromion and the clavicle bone protects the joint from wear and tear. When the cartilage is used more than its capability, it leads to overuse acromioclavicular joint injury. 

Depending on the tear, acromioclavicular injury can be categorized into:

  • Type I: slight tear in the acromioclavicular ligament, but no damage to the coracoclavicular ligament
  • Type II: complete tear in the acromioclavicular ligament, but no tear in the coracoclavicular ligament
  • Type III: both acromioclavicular and coracoclavicular ligaments get torn completely 
  • Type IV: both the ligaments are torn and there is a posterior displacement of the clavicle 
  • Type V: both the ligaments and the origin of the deltoid is torn, leading to extreme instability of the acromioclavicular joint
  • Type VI: inferior displacement of the clavicle into the subcoracoid position


What causes Acromioclavicular Joint Injury?

The most common cause of acromioclavicular joint injury is the direct force applied to the major part of the acromion. Impact of fall on the arm sprains the ligaments leading to injury. If the force is too much it can also damage the coracoclavicular ligament.

An indirect force, although uncommon, can also be the reason. Force transmitted up the arm because of fall on the outstretched hand leads to displacement and stress on the ligaments. The coracoclavicular ligaments remain unaffected. 


It has been observed that nearly 10% of the injuries are caused due to collision sports or accidents


Symptoms of Acromioclavicular Joint Injury

  • Pain and swelling in the shoulder 
  • Soreness and tenderness in the affected area of the joint
  • Loss of strength and inability of the shoulder to function properly
  • Inability to perform a range of motion in the affected shoulder
  • Visible bump or deformity in the shoulder
  • Pain while sleeping on the affected area
  • Discomfort performing daily activities  

In severe cases, the collar bone can be seen out of place.


Diagnosis of Acromioclavicular Joint Injury

Diagnosis of acromioclavicular injury begins with an in-depth review of the patient’s medical history followed by a physical examination where the doctor will check for soreness and deformity in the shoulder. It is likely for swelling or bruising to occur in the joint.  The doctor will observe the entire clavicle to check for the possibility of fractures in the collar bone. Simple shoulder tests will be carried out to assess the strength and the range of motion of the shoulder.

X-rays are sufficient in diagnosing acromioclavicular injury as it helps in showing the displacement of the joint. MRIs and ultrasounds are suggested as they show the damage and tear caused to the ligaments of the bones. They also help in locating its exact position and gauge the severity of the case.


Treatment for Acromioclavicular Joint Injury

Treatment of the injury depends on the severity of the case. 

Non-operative methods of treatment are recommended first. This includes ice packs and putting the arm into shoulder slings to decrease motions and medications to help with the pain. Physical therapy is highly advised as it helps in restoring the range of motion, regain stability and help the shoulder to return to its full function.

Type I to III do not require surgical intervention and can be treated through conservative methods. Type IV to VI requires surgical intervention.


 Acromioclavicular injuries can be managed conservatively to a greater extent. Nevertheless, to assess the severity of the injury it is necessary to get it checked by an orthopedic surgeon. The recovery period ranges from weeks to months depending on the patient’s case and their ability to heal.