Table 2

Description and diagnosis of acromioclavicular joint separations provided by Reid et al11 as described by Rockwood et al14

GradesDescriptionTestsImaging
ISprain of AC ligaments. The AC and CC are intactNo stability of clavicle detected on stress testsX-ray normal
IIAC ligaments are ruptured, CC ligaments are intact12Clavicle is unstable to direct stress testLateral clavicle may be slightly elevated, negative stress views on X-ray
IIIComplete disruption of the AC and CC ligaments without significant disruption of the deltotrapezial fascia12Deformity present with clavicle appearing elevated (acromion depressed), clavicle unstable in vertical and horizontal planesSeparation of the clavicle from the acromion especially evident with stress X-ray
IVDistal clavicle is posteriorly displaced into the trapezius musclePosterior deformity presentDisplaced clavicle evident on axillary X-ray view
VMore severe form of grade III. Complete disruption of the AC and CC ligaments with disruption of the deltotrapezial fasciaSignificant tenting or pseudolateral clavicle elevation, downward displacement of the scapularTwofold to threefold increase in the CC distance or a 100–300% increase in the clavicle to acromion distance on X-ray
VIInferior displacement of the distal clavicle, either subacromial or subcoracoidSevere trauma, usually accompanied by other significant injuries
  • AC, acromioclavicular; CC, coracoclavicular.