ACJ Instability

Shoulder Conditions

ACJ Instability 

The pain and other symptoms of acromioclavicular joint (ACJ) instability can disrupt your daily activities and prevent you from getting a good night’s rest.  

Sports Med London’s experts offer treatment for minor injuries and acute and chronic cases of ACJ instability. 


What Is The ACJ? 

You will find your ACJs at the top of your shoulders, where the outer ends of your collarbones (lateral clavicles) meet part of your shoulder blades (the acromion). The joint helps stabilise the shoulder during movement. 

The joint is surrounded by a thin capsule, which helps protect it. The ligaments that support the ACJ include the conoid and trapezoid ligaments, which together are the coracoclavicular ligaments, and the acromioclavicular ligament. 


ACJ Injuries 

Falling onto the point of the shoulder is the most common cause of ACJ injuries. Most cases are simple sprains in which the ligaments that help stabilise the joint tear slightly, and they do not cause ACJ instability. 


Symptoms Of ACJ Instability 

Injuries that affect the joint capsule and disrupt the ligaments can cause ACJ instability. Common symptoms include: 

  • Pain on the top of the shoulder and just below the collar bone 
  • Bruising and a lump at the top of the shoulder 
  • Pain when reaching across the body at shoulder level, such as when putting on a seatbelt 
  • Pain when reaching above shoulder height 
  • Pain when lying on the side of the affected side 
  • Shoulder weakness 
Instability Page


Diagnosing ACJ Instability 

Our specialist will ask you how the injury happened, and they will examine your shoulder carefully when diagnosing ACJ instability. They also will send you for an X-ray to determine whether the joint is dislocated, partially dislocated (subluxed), or fractured. 

If the X-ray does not show anything abnormal and the specialist suspects you might have other injuries to the joint, they will send you for an MRI scan of your shoulder as you might have a rotator cuff tear. If there is nothing abnormal in the X-ray and the specialist might diagnose an ACJ sprain. 


Treating ACJ Instability 

Our specialist will take various factors into account when recommending treatment for ACJ instability. The level of impairment, extent of displacement, and age of the injury are some of those factors.  

Minor injuries such as simple sprains usually do not require much treatment beyond simple painkillers, ice, and a course of physiotherapy. You might need to use a sling for a few days. 

Surgical treatment usually is recommended for more significant injuries. The surgery may be arthroscopic (keyhole) or open if the treatment is early intervention. In more severe cases, the open surgery would involve a reconstruction of the ACJ. Your shoulder will be immobilised in a sling for several weeks after surgery. Our physiotherapist will give you a tailored rehabilitation programme under the surgeon’s supervision. 



Technical Information:

What is ACJ (Acromioclavicular Joint) Instability?

The acromioclavicular joint (ACJ) lies at the top of the shoulder and is where the outer end of the collarbone (lateral clavicle) meets part of the shoulder blade (acromion). ACJ instability occurs when the surrounding joint capsule and the two ligaments connecting the clavicle (collarbone) to the coracoid (knobbly part of the shoulder blade that lies in the front) known as the Conoid and Trapezoid ligaments are completely disrupted. 


How do ACJ injuries occur?

Most injuries are simple sprains that occur following a fall onto the point of the shoulder. The ligaments that control joint stability may be partly torn in which case they will often settle with analgesia, applied ice and a course of physiotherapy. Occasionally a sling may be given for a short period. These do not result in ACJ instability.


What symptoms occur with ACJ instability?

Often an individual will have a mechanism of injury such as a fall and complain of pain on the top of the shoulder and in the front just below the clavicle. They may describe a visible “lump” or deformity at the top of their shoulder and have bruising. An individual will complain of pain when reaching for items above shoulder level and across their body at shoulder level such as the seatbelt in a car. There may be pain when lying on the affected side at night. They may complain of difficulty performing activities or work at shoulder level or above and may complain of weakness.


How is ACJ instability diagnosed?

This is based on the mechanism of injury and a careful physical examination. Plain X-rays will confirm if the ACJ is dislocated, subluxed or fractured. If no abnormality is present on X-rays and an individual is tender at the ACJ following a fall then a diagnosis of an ACJ sprain is often made. If there is a suspicion of other injuries an MRI scan of the shoulder may be requested for example to exclude a rotator cuff tear.


How is ACJ Instability treated? Surgical VS Non-Surgical management

This is dependent on a number of factors including the level of instability or impairment, extent of deformity (displacement) on X-rays, the type or classification (complexity) of the injury, whether the injury is acute (recent) or old (chronic) and the level of activity an individual wishes to return to.

Generally, sprains or minor injuries to the ACJ are treated non-surgically (conservatively) with analgesia, ice, a sling, and physiotherapy.

For more significant injuries surgery is often recommended and the type of surgery is decided on whether the injury is acute or chronic. If early intervention is performed this may be arthroscopic or open and aims and reducing the dislocated ACJ preferably within the first two weeks of injury. If the decision for surgery delayed such as after trialling conservative treatment or an individual presents two weeks after injury, then surgery usually involves a reconstruction. This is performed as an open procedure where the dislocated ACJ is reduced using a graft which may be synthetic or biological tissue.

Following surgery, the shoulder is immobilised in a sling for several weeks and a tailored physiotherapy rehabilitation programme with a specialist shoulder physiotherapist is commenced under the supervision of the surgeon.