ACJ Arthritis

This leaflet provides general information to help you understand ACJ arthritis and the available treatment options.

Not everyone with ACJ arthritis needs surgery.

At the heart of my practice is Shared Decision-Making. Whether we pursue conservative management (Plan A) or surgical intervention (Plan B), the goal is to create a tailored treatment plan that aligns with your lifestyle, values, and functional goals.

The Anatomy of the Shoulder Joint

The shoulder is one of the most complex joints in the body, relying on several structures working together.

How the Shoulder Works

Three main bones form the joint:

• Humerus (upper arm bone)
• Clavicle (collarbone)
• Scapula (shoulder blade)

The Labrum (Stabilising Ring)

A rim of rubbery tissue that deepens the shallow shoulder socket — like a "bumper" or suction cup that keeps the joint stable and prevents dislocation.

The Rotator Cuff

Four deep muscles keep the ball centred in the socket and let you lift and rotate your arm:

• Supraspinatus
• Infraspinatus
• Subscapularis
• Teres Minor

The Four Key Joints

• Glenohumeral Joint – the main ball-and-socket joint
• Acromioclavicular (AC) Joint – collarbone meets shoulder blade
• Subacromial Space – tunnel above the rotator cuff
• Scapulothoracic Joint – shoulder blade glides over rib cage

The "Cushioning" (Articular Cartilage)

A smooth, slippery coating on the ball and socket surfaces that lets the bones glide over each other without friction, for pain-free movement.

What Is ACJ Arthritis?

ACJ arthritis is wear and tear of the small acromioclavicular joint at the top of the shoulder, where the collarbone meets the shoulder blade. Over time the smooth joint lining wears down, causing pain and stiffness — often alongside subacromial impingement or rotator cuff problems.

The AC Joint

A small joint doing a big job:

• Sits at the very top of the shoulder
• Links the collarbone to the shoulder blade (acromion)
• Loaded heavily by overhead and across-body movement

Causes

Wear develops through use and injury:

• Repetitive use – constant strain, especially overhead
• Occupation and sport – weightlifting, building work
• Post-injury – after previous joint separations
• Often linked with impingement, bursitis or cuff tears

Symptoms & Examination

Symptoms

• Pain and tenderness at the top/front of the shoulder
• Worse overhead, across the chest, or lying on that side
• Clicking, snapping, or a visible bump over the joint

Examination

• Tender AC joint on palpation
• Pain on compressing the joint (arm across chest)
• Clinical examination often more helpful than scans

Diagnosis

• X-rays – identify joint degeneration
• Ultrasound / MRI – associated soft-tissue conditions

Plain X-ray

MRI

Treatment Options: A Shared Decision

I will discuss all available treatment options with you, explaining the benefits and risks of each. Your preferences, values, and lifestyle will be considered as we work together to create a treatment plan best suited to your needs — this shared decision-making process ensures you are fully informed and involved in your care.

Treatment Depends On

• Severity of pain and impact on sleep
• Associated impingement, biceps or cuff problems
• Response to injections
• Your activity demands

Plan A — Non-Surgical

Many people improve with:

• Rest: and modification of aggravating activities
• Pain Control: regular painkillers for pain relief
• Physiotherapy: rehabilitation for mobility and strength
• Injection: guided cortisone – relief, and helps confirm the AC joint as the source

Plan B — Surgical

Considered when…

• Persistent Pain: despite appropriate non-surgical treatment
• Daily Life: symptoms affecting activities or sleep
• Operation: arthroscopic ACJ excision – the most common procedure
• Approach: keyhole removal of the worn joint surface, sometimes may need an open approach
• Details: explained fully in a separate leaflet
• The Procedure: known as Arthroscopic ACJ Excision, this keyhole procedure removes a few millimetres of the worn end of the collarbone so the joint surfaces no longer grind. A separate leaflet will be provided for the surgery.

Management Pathway

Questions You May Wish to Ask

• What treatments should I try first?
• How long should I try them for?
• What improvement can I expect?
• What happens if I don't have surgery?