AC Joint Injury
The acromioclavicular (AC) joint sits at the top of the shoulder where the collarbone meets the bony tip of the shoulder blade. It’s commonly injured in falls onto the point of the shoulder or outstretched hand — frequent in rugby, cycling, AFL and martial arts. An AC joint injury is sometimes called a “shoulder separation” (distinct from shoulder dislocation).
Grading AC Joint Injuries
AC joint injuries are graded 1–6 based on severity:
- Grade 1: Sprain of the ligaments, joint intact, minimal displacement
- Grade 2: Partial tear — some step deformity, joint still partly stable
- Grade 3: Complete ligament disruption, visible bump at the joint
- Grades 4–6: Severe displacement — usually require surgical assessment
The majority of injuries are grades 1–3 and are managed conservatively with physiotherapy.
Symptoms
- Pain and tenderness directly at the top of the shoulder
- A visible bump or step at the AC joint (grades 2–3)
- Pain lifting the arm across the body (horizontal adduction)
- Difficulty lying on the affected shoulder
- Weakness and restricted shoulder movement
Treatment
Acute Phase (Week 1–2)
- Sling for comfort in severe cases (avoid prolonged use)
- Ice and relative rest
- Gentle range of motion to prevent stiffness
Rehabilitation
- Progressive shoulder strengthening targeting rotator cuff and scapular stabilisers
- AC joint and glenohumeral joint mobilisation
- Taping to support the joint and reduce pain
- Gradual return to overhead and loading activities
Return to Sport
We use objective strength and function testing to determine safe return to contact sport, and work with you on protective taping strategies where appropriate.
