Summary

Acromioclavicular joint (ACJ) injury is a common shoulder injury resulting from direct trauma to the point of the shoulder, typically from falls (cycling, horse-riding) or contact sports (rugby, ice hockey). The injury involves damage to the AC ligaments and, in more severe cases, the coracoclavicular (CC) ligaments. ACJ injuries are classified using the Rockwood classification (Types I-VI) based on the degree of ligament disruption and clavicle displacement. Most injuries (Types I-II) are treated conservatively with excellent outcomes. Type III is controversial, with initial conservative management favoured for most patients except high-demand athletes. Types IV-VI typically require surgical reconstruction.

Key Facts

• Definition: Injury to the acromioclavicular and/or coracoclavicular ligaments
• Mechanism: Direct blow to the shoulder point (FOOSH less common)
• Classification: Rockwood I-VI
• Most common types: I-III (95% of ACJ injuries)
• Key sign: Step deformity, "Piano Key" sign
• First-line treatment (I-II): Conservative (sling, analgesia, physiotherapy)
• Surgical threshold: Types IV-VI; selected Type III

Clinical Pearls

"Piano Key" Sign: In Type III+ injuries, pushing down on the prominent lateral clavicle allows it to descend, then it springs back up when released — like pressing a piano key.

The Type III Dilemma: Type III management is controversial. Most patients do well with conservative treatment. Consider surgery for high-demand athletes, manual workers, or those who fail conservative management after 3-6 months.

Zanca View: The best X-ray for ACJ assessment is the Zanca view (10-15° cephalic tilt). Standard AP views fail to show the ACJ adequately.

Why This Matters Clinically

ACJ injuries are common in active young adults and can cause persistent pain and weakness if mismanaged. Accurate classification guides treatment. Conservative management is appropriate for most, but surgical indications must be recognised. Chronic symptomatic ACJ injuries can be addressed with delayed reconstruction.

Structured Approach

General:

• Observe both shoulders from front and above
• Compare symmetry
• Note any deformity or swelling

Inspection:

• Step deformity (lateral clavicle prominence)
• Swelling/bruising over ACJ
• Skin integrity (tenting, open injury)

Palpation:

• Tenderness over ACJ
• Step between clavicle and acromion
• Clavicle shaft (exclude fracture)
• Scapula and ribs

Range of Motion:

• Active ROM often limited by pain
• Cross-body adduction reproduces pain

Special Tests

Natural History

• Type I-II: Excellent outcomes with conservative management
• Type III: 70-90% do well conservatively; 10-30% have persistent symptoms requiring surgery
• Type IV-VI: Poor outcomes without surgery

Outcomes with Treatment

Prognostic Factors

Good Prognosis:

• Lower grade injury (I-II)
• Early treatment
• Good physiotherapy compliance
• Low-demand patient

Poor Prognosis:

• High-grade injury (V-VI)
• Delayed presentation (chronic)
• High-demand athlete / manual worker
• Previous ACJ injury
• Non-compliance with rehabilitation

Key Guidelines

1. ISAKOS Upper Extremity Committee Consensus (2014) — Classification and management of acromioclavicular joint injuries. ISAKOS
2. BOA Standards (BESS) — British Elbow and Shoulder Society guidance.

Landmark Trials

Canadian Orthopaedic Trauma Society (2015) — Type III ACJ injuries: Operative vs Non-Operative

• 83 patients randomised
• Key finding: No significant difference in functional outcome at 2 years
• Key finding: Surgical group had better cosmetic outcome but more complications
• Clinical Impact: Supports conservative management as first-line for Type III

Beitzel et al. (2013) — Surgical techniques comparison

• Systematic review of surgical techniques
• Key finding: No single technique demonstrated clear superiority
• Clinical Impact: Technique selection based on surgeon experience and patient factors

Evidence Strength

What is an ACJ injury?

The acromioclavicular joint (ACJ) is where your collarbone meets the top of your shoulder blade. An ACJ injury (sometimes called a "separated shoulder") happens when you fall directly onto the point of your shoulder, stretching or tearing the ligaments that hold these bones together. This is different from a dislocated shoulder (where the ball comes out of the socket).

Why does it matter?

The severity of the injury determines how well it heals. Most ACJ injuries are mild (Type I-II) and heal very well without surgery. More severe injuries may leave a visible "bump" on top of your shoulder where the collarbone sits higher than normal, and some may need surgery to restore function.

How is it treated?

1. Mild injuries (Type I-II): Rest in a sling for comfort, painkillers, and physiotherapy. You can usually return to normal activities within 2-4 weeks.

2. Moderate injuries (Type III): Usually treated with a sling and physiotherapy first. Most people recover well, but if pain and weakness persist after 3-6 months, surgery may be considered.

3. Severe injuries (Type IV-VI): Usually require surgery to repair or reconstruct the ligaments and hold the collarbone in the correct position.

What to expect

• Pain and swelling are worst in the first few days
• You may have a permanent "bump" on top of your shoulder — this is usually cosmetic and doesn't cause problems
• Physiotherapy is important to regain strength and movement
• Return to contact sports typically takes 6-12 weeks for moderate injuries

When to seek help

Contact your doctor or return to hospital if:

• Your pain is getting worse despite painkillers
• The skin over the bump becomes very tight, red, or breaks
• You have numbness or weakness in your hand or fingers
• You notice increasing swelling or deformity

The "Painful Shoulder" Station

1. Look (The Step)

• Expose both shoulders.
• The Step Deformity: Is the lateral end of the clavicle prominent? (Type III-V).
• Skin: Any tenting? (Grade V - Emergency).
• Scapula: Winging? Dyskinesis?

2. Feel (The Tender Spot)

• Palpate the SC Joint -> Clavicle -> AC Joint.
• Accuracy: ACJ tenderness is sensitive but not specific.
• The Piano Key Test:
  • Push down on the distal clavicle.
  • If it "bobs" up and down, the CC ligaments are gone (Grade III+).
  • Tip: Do this gently. It hurts.

3. Move (The Painful Arc)

• High Arc Pain: Pain at 170-180° abduction (Terminal arc) is ACJ. (Pain at 60-120° is Subacromial).
• Scarf Test: Cross-body adduction. "Reaching for the scarf". Compresses the ACJ. Pain = Positive.

Viva Questions:

• Q: Classify ACJ Injuries.
  • A: Rockwood Classification. Types I-VI based on displacement and ligament status.
• Q: Why do we take a Zanca View?
  • A: It is an AP with 10-15° Cephalic Tilt. It removes the scapular spine overlap to visualize the ACJ clearly.
• Q: Management of Type III?
  • A: Controversial. Evidence suggests EQUAL functional outcomes for Conservative vs Surgical. Conservative first ($/Risk/Recovery). Surgery for elite overhead athletes.
• Q: What structures are torn in Type III?
  • A: The AC ligaments, the CC ligaments (Conoid/Trapezoid), and the deltotrapezial fascia.

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Consult an orthopaedic surgeon for ACJ injury management.