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AC Joint Sprain Cheat Sheet by

Information sheet for AC Joint Sprain


Superior, inferior, anterior, posterior AC ligaments = Prevents A/P shear and provides horizontal stabil­isation - superior most important for stability
Coracl­avi­cular ligaments = Conoid and Trapezoid - Resists superior and inferior transl­ation

Rockwood Classi­fic­ation

Type I – mild, unsepa­rated sprain of the AC ligaments with no disruption of the coraco­cla­vicular ligaments.
Type II – complete disruption of the AC ligaments with joint separation (less than 4 mm or 40% differ­ence) and sprained but intact coraco­cla­vicular ligaments.
Type III – complete disruption of AC and coraco­cla­vicular ligaments with joint separation and inferior displa­cement of the shoulder complex.
Type IV – complete disruption of AC and coraco­cla­vicular ligaments with posterior displa­cement of the clavicle through the fibers of the trapezius, and detachment of deltoid and trapezius muscles from the distal clavicle.
Type V – complete disruption of the AC and coraco­cla­vicular ligaments with signif­icant inferior displa­cement of the shoulder complex from the clavicle as compared to a typical Type III injury.
Type VI – complete disruption of the AC and coraco­cla­vicular ligaments, and the clavicle has dislocated inferi­orly, below the coracoid process.

Mechanism of injury

- Fall onto the shoulder with arm in an adducted position
- FOOSH/­Elbow
- Makes up 40-50% of athletic shoulder injuries at 2-4th decade of life
- Rugby, Ice hockey, football, wrestling players are more suscep­tible


- Pain and swelling on antero­sup­erior aspect of the shoulder after trauma
- Symptoms start in the traps,­sho­ulder and neck but move to the AC joint
- Painful with bench pressing, dips or laying on the affected side
- Bruisi­ng/­def­omity on clavicular prominence

Diagnostic findings

- Swelling, bruising and deformity on clavicular prominence
- Tenderness over AC
- Feeling of giving way on palpation of distal clavicle (+ve Piano Key sign)
- ROM painful and limited - abduction most affected
- +ve Cross body adduction
- +ve BvR
- +ve Paxino
- +ve Buchberger test
- Associated with fractured clavicle, imping­ement syndromes and neurov­ascular insults
- Consider active vs passive ROM - Rotator cuff
- Buchberger test distin­guishes subacr­omial imping­ement from AC joint sprain (more pain in external rotation)
- Evaluate entire clavicle and SC for other injuries
- Perform full neurov­ascular exam on affected side


- Clavicular f#
- Rotator Cuff lesion
- Shoulder Anterior imping­ement syndrome
- Shoulder disloc­ation
- Labral injury
- Osteolysis of distal clavicle
- Neoplasm
- Rheuma­tologic disease
- Cervical spine/­vis­cer­oso­matic referral
- Shoulder osteoa­rth­ritis
- Adhesive Capsulitis
- Erb Duchenne
- Septic Arthritis


AP, lateral, and axillary lateral views
- Not often apparent on x-ray - Zanca view (tilting of beam 10-15 degrees caudal and bilateral AP views), weighted stress views
- MRI only used to rule out other pathol­ogies of the shoulder
- X-ray shows AC joint separation (type 3) due to ligament injury


Grade I + II - Protec­tion, immobi­lis­ation (sling for 3-10 days), mobility and streng­thening
- Passive mobility exercises (avoid exercises that involve behind back internal rotation, crossbody adduction and forward elevation)
- Streng­thening (closed chain scapula stability exercises - scapula clocks
- Prognosis is favourable
- Usually regains motion by six weeks and regain normal function within 12 weeks
- Surgery for IV-VI types (six week immobi­lis­ation with up to six months recovery time)
- AC joint arthritis and joint pain can occur in future
- Type III-VI should have regular appoin­tments by a orthop­aedic surgeo­n/p­hys­ician


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