ACJ Instability

Shoulder Conditions

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.


Instability Page

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.