AC Joint Injury: Symptoms, Treatment and Recovery

01Anatomy

Where the acromioclavicular joint is

Cambridge University Hospitals (CUH) explains that the acromioclavicular joint (ACJ) sits between the top of the shoulder blade, called the acromion, and the far end of the collarbone (clavicle). Ligaments and muscles hold the collarbone to the shoulder blade, keeping the joint stable.

In an AC joint injury, these ligaments are damaged. Chelsea and Westminster Hospital explains that, depending on how severe the injury is, this may cause swelling, a bump or, if the joint has been dislocated, a significant protrusion at the end of the collarbone. Our guide on collarbone pain covers other problems in this area.

02Types of injury

Sprain and separation versus other shoulder injuries

AC joint injuries are often described as a sprain when the ligaments are stretched or partly torn, and as a separation or dislocation when the collarbone loses its normal contact with the acromion. Doctors grade the injury after examination and X-rays, according to how much the bones have moved and which ligaments are involved.

An AC separation is not the same as a dislocation of the main shoulder joint, where the ball of the upper arm bone comes out of its socket. It is also different from a collarbone fracture or a rotator cuff injury, although these can cause pain in similar areas. Our guides on shoulder subluxation and a shoulder labral tear describe other shoulder injuries.

03Symptoms

Falls, blows and symptoms

AC joint injuries typically follow a fall onto the shoulder or a direct blow, for example in contact sports or cycling. Common symptoms described in the NHS leaflets include:

• pain and tenderness at the top of the shoulder, over the end of the collarbone
• swelling and bruising in this area
• a bump or step at the end of the collarbone, especially in more severe injuries
• discomfort when lifting the arm or reaching behind the head

Chelsea and Westminster notes that pain and tenderness usually settle gradually over several weeks, and that reaching and lifting may be uncomfortable but are safe to try once the injury has been assessed.

04The bump

Why a bump cannot determine the grade at home

A visible bump is often what worries people most. However, its size cannot tell you on its own how severe the injury is or whether other structures are damaged. Swelling can make a mild injury look worse, and fractures around the shoulder can cause similar pain.

For this reason, an injury with significant pain, swelling or deformity after a fall should be examined rather than self-diagnosed, and you should not try to push the bump back into place or bind it tightly at home. Chelsea and Westminster also explains that a visible bump may remain after recovery, even when the shoulder works well.

05Assessment

Clinical examination and selected imaging

Diagnosis is based on how the injury happened, an examination of the shoulder and X-rays, which show the position of the collarbone and rule out fractures. CUH explains that the shoulder may be X-rayed again at the specialist appointment if the first images need checking, and that the shoulder specialist then discusses options for managing the injury.

If you have been given a fracture clinic or shoulder specialist appointment, CUH stresses that you should not miss it. The advice in the rest of this guide is for people whose injury has already been assessed; it is not permission to move or load a shoulder that has not been checked after a significant injury.

06Early care

Protection and comfort after assessment

After assessment, both NHS leaflets describe similar early care:

• a sling to support the arm in a comfortable position for a short time; Chelsea and Westminster explains that it only helps with pain and does not change the speed of recovery or the position of the bones
• ice wrapped in a tea towel for about 20 minutes, three to four times a day, to reduce swelling and pain
• simple over-the-counter painkillers as needed, so that you can keep the shoulder moving gently
• not driving or cycling while wearing the sling

Chelsea and Westminster suggests gradually stopping the sling over 2 to 3 weeks as pain improves, using the shoulder as much as pain allows. CUH says the sling may only be needed for a few days.

07Movement

Progressive movement and physiotherapy

CUH advises starting to use the arm within the limits of pain, particularly the hand, wrist and elbow. Chelsea and Westminster recommends gentle exercises to overcome stiffness, removing the sling first and stopping if they are too painful. Its leaflet describes pendulum exercises, leaning forward with support and gently swinging the arm forwards and backwards, across the body and in circles, starting with a few repetitions and building up.

As pain settles, strength and movement are progressed according to how the shoulder responds. Physiotherapy can help when stiffness, weakness or loss of confidence persist. In our physiotherapy practice in Bilbao we offer individual rehabilitation for adults after medical assessment (consultations are in Spanish).

08Surgery

When specialist surgery may be considered

Most AC joint injuries do not need an operation. CUH reports that around 80% of patients in its service get better without surgery, especially those whose jobs or hobbies do not involve overhead or manual work. The shoulder specialist discusses whether surgery could help in your case, for example after more severe separations or when symptoms do not settle.

Chelsea and Westminster notes that occasionally the injury may fail to settle even after several months. If significant pain, a feeling of instability, reduced strength or loss of confidence in the shoulder continue, it advises contacting the clinic for further advice. These are the situations in which a specialist review is most useful.

09Sources

Where the sources differ

The two NHS leaflets agree on the main approach but differ in emphasis and detail:

• Sling. CUH mentions a sling for a few days; Chelsea and Westminster suggests gradually stopping it over 2 to 3 weeks as pain improves. The right time depends on the injury and on your pain.
• Contact sport. CUH advises avoiding contact sports for 8 to 12 weeks, as guided by the consultant; Chelsea and Westminster does not give a time frame. Return should be agreed with your clinician.
• Recovery. Chelsea and Westminster says the shoulder can twinge for up to 3 months and symptoms may take several months to settle. CUH focuses on the specialist review.
• Wording. The CUH leaflet mentions swelling at the “fracture site”, but describes a ligament sprain; an AC sprain is not a fracture. Neither leaflet gives a full grading system.

10Summary

In summary

An AC joint injury is damage to the ligaments joining the collarbone to the shoulder blade, usually after a fall or blow. It causes pain, swelling and sometimes a bump at the top of the shoulder. It needs a clinical assessment, often with X-rays, to confirm the injury and rule out a fracture.

Most people recover without surgery, with a sling for comfort for a short time, ice, pain relief and gradual exercises, although symptoms can take several months to settle and a bump may remain. A simple record of the tasks you find difficult, such as reaching overhead, lifting or sleeping on that side, and how they change over the weeks helps guide your return to work and sport and your review with the specialist.