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AC joint injury, Rockwood grades, rehab and when surgery is the answer.

A common shoulder injury from a fall on the point of the shoulder. Most settle with a sling and staged rehab; a small number need surgical stabilisation to get back to full function.

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A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Editorial team

    Written by our editorial team from the UK sources listed on each page.

  • 02

    Sourced from guidance

    Cross-checked against BOA, BESS and peer-reviewed shoulder literature you can see at the end.

  • 03

    Current for 2026

    Reflects modern practice on Rockwood grading, hook plate use, tightrope fixation and CC ligament reconstruction.

Key facts

AC joint injury at a glance.

The essentials, in plain English: what the injury is, how it is graded, and how it is treated in the UK today.

  • What it is

    Injury to the acromioclavicular joint at the top of the shoulder, ranging from mild sprain to full dislocation with ligament rupture.

  • Typical mechanism

    A fall on the point of the shoulder or a direct contact-sport blow, driving the acromion downward relative to the clavicle.

  • How it is graded

    The Rockwood classification, Types I to VI, based on the pattern of ligament injury and direction of clavicle displacement.

  • First-line imaging

    AP and Zanca X-rays of both shoulders. MRI is selective, mainly to confirm ligament rupture or plan surgery.

  • Most cases

    Types I and II are managed conservatively with a broad-arm sling, analgesia and staged physiotherapy.

  • When surgery is used

    Types IV, V and VI need surgical repair. Type III sits in a grey zone, with surgery reserved for selected overhead athletes.

Why this guide matters

Grade the injury, then choose the path.

The Rockwood grade sets the plan. Most ACJ injuries do not need surgery, but a small number absolutely do, and rushing the decision either way costs function.

  • Grading changes everything

    Rockwood I to II settle with a sling and rehab. IV to VI need surgery. Type III sits in between and is decided case by case.

  • Imaging is targeted, not routine

    AP and Zanca X-rays of both shoulders confirm the grade. MRI is reserved for high-grade or late-presenting injuries and surgical planning.

  • Rehab is the workhorse

    Whether or not you have surgery, structured physiotherapy is what returns the shoulder to sport and work.

How the diagnosis is made

From the fall to a Rockwood grade.

The steps a UK A&E or shoulder specialist will normally follow, in order, so you know what to expect and why.

  1. 01

    Assessing

    History and mechanism

    Fall onto the point of the shoulder, rugby or cycling crash, direct impact. The story often points to the diagnosis before you look.

  2. 02

    Assessing

    Inspection for deformity

    A visible step-off at the top of the shoulder, prominent distal clavicle, bruising or skin tenting suggests a high-grade injury.

  3. 03

    Assessing

    Focused palpation and tests

    Tenderness over the ACJ, painful cross-body adduction and Paxinos test help localise the injury away from rotator cuff or SLAC pathology.

  4. 04

    Confirming

    AP and Zanca X-rays

    Bilateral views compare coracoclavicular distance and clavicle displacement side to side. The Zanca view angles the beam 10 to 15 degrees cephalad for a clearer ACJ.

  5. 05

    Confirming

    Selective MRI

    MRI is not routine. It is used to confirm CC ligament rupture, assess rotator cuff or SLAC lesions, or plan reconstruction in late-presenting injuries.

  6. 06

    Planning

    Rockwood classification

    Grade the injury Type I to VI. This determines whether the shoulder can be rehabilitated in a sling or needs surgical stabilisation.

  7. 07

    Planning

    Shared decision for Type III

    Type III sits between conservative and surgical care. The decision weighs sport, dominant arm, overhead demand and cosmetic concern before choosing a path.

Typical timeline: from A&E to a settled plan within one to two weeks.

Symptoms

What an AC joint injury looks like.

The classic pattern of tip-of-shoulder pain, a visible step-off and painful overhead reach. And the features that mean it is time to escalate.

  • Pain over the ACJ

    Sharp, localised pain at the tip of the shoulder, worse on reaching across the body or lifting overhead.

  • Visible step-off

    The distal clavicle sits proud of the acromion, giving a characteristic bump that reduces on downward pressure.

  • Bruising and swelling

    Local swelling and bruising over the top of the shoulder within 24 to 48 hours of injury.

  • Loss of overhead range

    Pain and weakness on abduction above 90 degrees, and on cross-body adduction, are typical patterns.

  • Positive Paxinos and cross-body tests

    Squeezing the ACJ from behind or forcing cross-body adduction reproduces the pain and helps confirm the source.

  • Posterior clavicle displacement

    A Type IV injury pushes the clavicle backwards through trapezius and needs urgent orthopaedic review.

  • Skin tenting or threatened skin

    A very high-riding clavicle with tented or blanched skin is a Type V or VI feature and a surgical indication.

  • Red flag - neurovascular signs

    Pins and needles, weakness or a cold pulseless arm suggest brachial plexus or vascular injury and need urgent A&E assessment.

Rockwood classification

Types I to VI, in plain English.

The Rockwood classification grades AC joint injuries by which ligaments are torn and how far the clavicle has displaced. It is the single most important framework for deciding treatment.

  • Type I

    AC ligament sprain

    Sprain of the AC ligaments without disruption. Normal X-ray. Treated in a sling for comfort and early rehab.

  • Type II

    AC ligament rupture

    AC ligaments ruptured, CC ligaments intact. Slight step-off and mild widening of the ACJ. Treated conservatively.

  • Type III

    Complete AC and CC rupture

    Both AC and CC ligaments ruptured with under 25 per cent clavicle displacement. Grey zone: rehab first for most, surgery for selected overhead athletes.

  • Type IV

    Posterior displacement

    Clavicle displaced posteriorly through trapezius. Almost always needs surgical reduction and stabilisation.

  • Type V

    Over 100 per cent displacement

    Gross superior displacement with skin tenting, over 100 per cent CC widening. A clear surgical indication.

  • Type VI

    Inferior or subcoracoid

    Very rare inferior or subcoracoid displacement, often with brachial plexus involvement. Needs urgent surgical reduction.

Treatment

How AC joint injuries are treated in the UK.

Sling and physiotherapy for Types I and II. Shared decision for Type III. Surgical stabilisation for Types IV to VI and for late-presenting injuries with a symptomatic step-off.

  • Broad-arm sling

    Type I and II injuries are supported in a sling for one to three weeks for comfort, alongside early pain relief and gentle range work.

  • Analgesia

    Paracetamol and a short course of anti-inflammatories, where appropriate, cover the acute inflammatory phase and let physiotherapy begin.

  • Structured physiotherapy

    Staged rehab from range of motion, through scapular control, into strength and, finally, sport-specific loading over 6 to 12 weeks.

  • Guided ACJ injection

    For selected chronic Type I to III cases with persistent pain, an ultrasound-guided steroid injection can settle the joint and support rehab.

  • Hook plate fixation

    A temporary metal plate hooks under the acromion and holds the clavicle reduced while the CC ligaments heal. Removed at 3 to 6 months.

  • Tightrope or endobutton

    A cortical button and suture construct reduces the clavicle to the coracoid, avoiding a second operation for metalwork removal.

  • CC ligament reconstruction

    For high-grade or delayed injuries the coracoclavicular ligaments are reconstructed with a semitendinosus or gracilis autograft or allograft.

  • Revision or salvage surgery

    Failed fixation, chronic instability or arthritis may need distal clavicle excision combined with a formal ligament reconstruction.

Late presentation

Beyond three months, primary fixation is rarely enough.

Once the CC ligaments have scarred, simple reduction and hook plate fixation tends to fail. A formal anatomic coracoclavicular ligament reconstruction using a semitendinosus or gracilis tendon graft, sometimes with distal clavicle excision, is the durable answer.

What this guide is based on

The sources behind every claim on this page.

UK and international specialist society standards and shoulder literature, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your A&E doctor, physiotherapist or shoulder surgeon knows your injury and history and can tell you which parts apply to you. If in doubt, get seen.

  • Rockwood CA. Injuries to the acromioclavicular joint. Rockwood and Green’s Fractures in Adults.

  • British Elbow and Shoulder Society (BESS). Consensus on management of acromioclavicular joint injuries.

  • British Orthopaedic Association (BOA). Standards for trauma - shoulder girdle injuries.

  • European Society for Surgery of the Shoulder and the Elbow (SECEC-ESSSE). ACJ injury consensus statements.

Red flags

When AC joint injury needs urgent attention.

Most AC joint injuries can be managed through the usual A&E and shoulder-clinic pathway. These are the situations that need faster escalation.

  • Neurovascular compromise

    Cold, pulseless or numb arm after injury needs immediate A&E and vascular review, not clinic follow-up.

  • Skin tenting or blanching

    A very high-riding clavicle threatening the skin is a surgical emergency to prevent breakdown and open injury.

  • Posterior displacement

    Rockwood Type IV injuries push the clavicle backwards through trapezius. They almost always need surgical reduction.

  • Open injury or laceration

    Any wound communicating with the joint needs urgent debridement and antibiotic cover in an orthopaedic setting.

  • Associated coracoid or clavicle fracture

    Combined bony and ligamentous injury changes the fixation plan and should be reviewed by a shoulder specialist.

  • Chest wall or scapular pain

    Persistent chest or scapular pain after a high-energy fall may indicate rib or scapula fracture that needs imaging.

  • Persistent instability at 3 months

    Ongoing pain, weakness and a symptomatic step-off beyond three months usually needs surgical reconstruction, not more rehab.

  • Suspected brachial plexus injury

    Weakness or sensory loss in a nerve territory after a high-energy shoulder injury warrants urgent neurophysiology and specialist review.

  • Failure to progress in rehab

    A shoulder that plateaus in structured physiotherapy at six to eight weeks should be re-imaged and reassessed by a shoulder surgeon.

Living with it

A treatable injury, with a clear rehab ladder.

Four things that make the biggest difference: early comfort, structured scapular work, a staged return to sport and a low threshold to escalate if the shoulder does not settle.

A quiet reminder

A visible bump is not the whole story.

Many patients live very happily with a permanent cosmetic step-off after Type III injuries. Function, not appearance, drives the decision to operate.

  1. 01 Early

    Rest the shoulder briefly

    A sling for one to three weeks in low-grade injuries protects the joint while letting early gentle range work begin.

  2. 02 Rehab

    Rebuild scapular control

    Structured physiotherapy focusing on the scapula and rotator cuff is the difference between a nagging shoulder and a strong one.

  3. 03 Return

    Stage your return to sport

    Non-contact drills first, then contact, then full match play. Rushing back doubles the risk of a repeat injury.

  4. 04 Long-term

    Watch for late instability

    If pain, weakness or a visible step-off persist beyond three months, ask for a shoulder specialist review to discuss reconstruction.

Frequently asked

Everything we get asked about AC joint injury.

Quick answers on grading, imaging, surgery and return to sport.

  • What is an AC joint injury?

    An acromioclavicular joint injury is damage to the small joint at the top of the shoulder where the clavicle meets the acromion. It ranges from a simple sprain of the AC ligaments through to complete rupture of both the AC and coracoclavicular ligaments with visible dislocation.

  • How is the injury graded?

    By the Rockwood classification. Type I is a sprain, Type II is AC ligament rupture with a partial step-off, Type III is complete AC and CC ligament rupture with less than 25 per cent displacement, Type IV is posterior displacement into trapezius, Type V is over 100 per cent displacement and Type VI is rare inferior or subcoracoid displacement.

  • Do I need an MRI?

    Usually no. AP and bilateral Zanca X-rays confirm most injuries and grade them. MRI is used selectively to confirm CC ligament rupture, look for associated rotator cuff or SLAC lesions, or plan reconstruction in late-presenting injuries.

  • Which grades need surgery?

    Types I and II are treated conservatively. Types IV, V and VI almost always need surgical stabilisation. Type III sits in a grey zone and is decided case by case, with surgery reserved for younger overhead athletes, manual workers with dominant-arm injuries and patients with persistent symptoms after rehab.

  • What does surgery involve?

    Acute high-grade injuries are stabilised with a hook plate, tightrope or endobutton construct, sometimes combined with CC ligament reconstruction. Delayed presentations, typically beyond three months, usually need formal coracoclavicular ligament reconstruction with a tendon graft rather than simple fixation alone.

  • When can I return to sport?

    Type I and II injuries usually return to non-contact activity within two to four weeks and contact sport by six to twelve weeks, guided by rehab milestones. After surgical stabilisation, return to contact sport is generally planned at four to six months with staged clearance from physiotherapy and the operating surgeon.

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