AC Joint Pain Treatment London | Private Ultrasound Diagnosis & Injections

AC Joint Pain Explained

Anatomy of the AC Joint & Surrounding Structures

The shoulder acromioclavicular joint (AC joint) is formed by the outer end of the collarbone (clavicle) and the acromion bone of the upper shoulder blade. Together with the acromioclavicular joint ligaments, this joint forms a structural roof overlying the rotator cuff tendons and the subacromial bursa, which themselves lie over and wrap around the top of the humeral head bone of the upper arm.

AC Joint pain symptoms

Patients suffering with AC joint pain tend to point to the local area of pain directly over the joint, which may radiate through the upper trapezius muscle bulk towards the neck. Pain tends to be felt with weight-bearing movements, pushing movements such as bench press and terminal shoulder press at the gym, or lifting the arm fully above the head.

Causes of AC Joint Pain

The AC joint transfers weight-bearing loads from the arm to the upper shoulder and spine and is required to rotate enough to allow us to place our hand behind our back and our arm above our head or across our body.

Due to the heavy loads placed on this small joint, it is common when ultrasound imaging the AC joint to observe degenerative changes, which appear as irregularity and roughness of the bony cortical margins of the AC joint, as well as some thickening of the joint capsule. Although degenerative changes to the AC joint seen on imaging are common, it is relatively uncommon for these degenerative processes to give rise to significant shoulder pain compared to more common shoulder pain types such as rotator cuff disorders and subacromial bursitis.

AC Joint Pain Diagnosis

An ultrasound scan can reliably diagnose AC joint pain when combined with a physical examination, although in some cases an X-ray may be required to exclude other conditions around this region.

AC Joint Ultrasound Guided Injections

How is an AC Joint Injection Administered?

When AC joint pain is present, an ultrasound-guided injection can be performed using an in-plane or out-of-plane technique. In the out-of-plane technique, a centreline is used to place the AC joint at the centre of the ultrasound image screen. After carefully assessing the required depth, the needle tip is introduced directly at the centre of the ultrasound probe so that the needle tip can be seen passing into the AC joint at the centre of the joint.

An alternative approach is an in-plane technique, with the ultrasound probe positioned transversely across the AC joint. The needle is introduced from the lateral aspect of the probe into the joint capsule, allowing visualisation of the injectate flowing into the joint.

What to do after your AC Joint injection

Needle Path & Post-Injection Pain
The AC joint can be accessed relatively easily under ultrasound guidance using either an out-of-plane or in-plane technique. Because of this, pain from the needle path itself is not usually a concern following an AC joint injection.
Depending on patient factors and how the AC joint appears under ultrasound, the steroid may be mixed with a low or higher volume of local anaesthetic. Depending on this volume, there should be little or no immediate post-injection pain. Very rarely, some patients may experience a post-injection flare, which is thought to occur when the steroid crystals react with the normal synovial fluid in the joint. While this is unlikely with an AC joint injection, it cannot be completely excluded.

Wound Care & Infection Risk
Due to the small needle site, avoid exposing it to dirty or public water (such as swimming pools) for 2 days after an AC joint injection to minimise infection risk.

Activity Guidance
Sensible activity modification should be followed for 2–3 days after the injection. If no significant problems are encountered, you can gradually increase your daily shoulder activities over the next 2 weeks. During the first 2 weeks, strenuous exercise and significant end-of-range overhead movements should still be avoided. After 2 weeks, if there are no issues, light exercise and overhead movements can be introduced in a sensible, graded manner.

Follow-Up
Following an AC joint injection, please contact me immediately if you experience any difficulties.

Other Treatments for AC Joint pain

Physical Therapy exercises for AC Joint pain

Physical Therapy exercises for AC Joint pain

AC Joint Pain | Evidence base

The majority of ACJ-related pain resolves with conservative treatment, and current evidence supports physiotherapy as a first-line approach. This typically includes scapular stability work, mobility, and general shoulder strengthening. Ultrasound-guided corticosteroid injections have been shown to offer effective short-term pain relief, especially for inflammatory flare-ups or in cases limiting rehab participation. Longitudinal studies suggest that injection plus rehab offers better outcomes than injection alone. Surgery, such as distal clavicle excision, is typically reserved for patients with persistent mechanical symptoms, structural joint damage, or trauma, and is not a routine first-line intervention. The evidence favours a conservative approach in the absence of clear structural disruption.