The acromioclavicular joint is a small joint located in close proximity to the shoulder joint. It is formed by the acromion process and the distal end of the clavicle. The joint is stabilized from above by the acromioclavicular ligament. Additional stabilization of this joint, as well as the stabilization of the clavicle relative to the scapula, is provided by the coracoclavicular ligaments, which extend between the distal end of the clavicle and the coracoid process of the scapula.

Diseases of this joint include degenerative conditions caused by overuse or trauma. However, the most common and requiring treatment is traumatic instability and dislocation of the joint.

Instability of the acromioclavicular joint is a condition that occurs as a result of direct trauma to the joint, such as a fall onto the shoulder with the upper limb adducted, for example during skiing, hockey, combat sports, rugby, or as a result of indirect trauma, such as a fall onto an extended upper limb. This trauma can result in partial or complete dislocation of the joint, which the patient may observe as elevation of the distal end of the clavicle. This is due to the rupture of the coracoclavicular and acromioclavicular ligaments.

Symptoms of acromioclavicular joint instability

The typical symptoms of acromioclavicular joint instability include local swelling and pain, which worsens with pressure on the shoulder from above. The “piano key sign” is often present, meaning that the distal end of the clavicle can be depressed and then rebounds back up when pressure is released. Movement of adduction or flexion of the shoulder joint above the level of the injury site increases pain, and loading of the affected limb increases the visible deformity and elevation of the clavicle.


The basis for the diagnosis is a patient history and clinical examination, which allows the physician to locate the site of the injury and exclude any damage to the shoulder joint. Specific tests are performed to make an initial diagnosis, which is subsequently confirmed with imaging studies.

To date, the standard diagnostic imaging study is an X-ray examination, which should be performed bilaterally for comparison of both joints. There are six types of injuries classified, with Types I and II not requiring surgical treatment, Type III, which may or may not require surgical treatment, and Types IV-VI, which are direct indications for surgical intervention.

The treatment of acromioclavicular joint instability depends on the type of injury.

For Type I-III injuries, conservative treatment is the preferred approach. This involves initial immobilization of the limb in a sling for 3 weeks, followed by progressive rehabilitation with restricted movements for 6 weeks.

For Type III injuries in non-athletes, conservative treatment is usually attempted. If symptoms such as instability and pain persist after 3 months of rehabilitation, particularly during overhead movements, a decision may be made to proceed with surgical treatment. There is a relative indication for surgery in active athletes or individuals involved in sports.

Type IV-VI injuries and symptomatic chronic instability require surgical treatment. The most commonly performed procedure is arthroscopic surgery, which is performed through several small incisions, usually two incisions about 1.5-2 cm above the clavicle and acromioclavicular joint. The surgery involves stabilizing and tightening the clavicle to the coracoid process using tapes and two titanium “buttons” attached from under the process and above the clavicle, as well as suturing and stabilizing the acromioclavicular joint with sutures or tapes. This also ensures alignment of the distal end of the clavicle with the acromion process. This procedure can also be performed using an open approach, with an incision of about 6-8 cm on the anterior surface of the joint. The procedure takes about 90 minutes.

After surgery, the limb is immobilized in a sling for 3 weeks. Rehabilitation with restricted movements is started during this time and continues for 6 weeks. Return to full sports activity takes about 6 months.

In the case of chronic shoulder joint instability, which lasts for more than 3 weeks from the injury, surgical treatment supplemented with reinforcement using a tendon graft taken from the patient’s knee joint area, for example, is recommended. This aims to reconstruct the acromioclavicular and coracoclavicular ligaments.

At MIRAI, the following individuals specialize in shoulder area:
Bartosz Dominik – material development for the website
Michał Drwięga