AC Joint Sprain

Acromio Clavicular Joint (ACJ) injury is most often caused by trauma following a fall directly onto the shoulder. These are commonly seen in rugby, after a bike accident or with a heavy fall onto the shoulder. The ACJ is also a common site of arthritic changes, particularly with a history of trauma.

Symptoms

ACJ is often graded depending on the severity of the injury using the Rockwood classification (see table below). It is important to establish the grade of your injury as there are different management approaches for each grade. X ray can be a useful tool in diagnostics but studies have shown that there are weak correlations between x ray findings and level of pain/disability experienced. It is vitally important that you are assessed to establish the extent of injury and any functional limitation to guide your management.

Rockwood Classification Definitions (adapted from Black, 2013)

Type 1: Sprain of AC ligamentsComments: Most common type. No instability
Type 2: Rupture of AC ligaments, Sprain of CC ligaments Comments: Clavicle unstable
Type 3:Rupture of AC ligaments, detachment of deltoid and trapezius muscles Comments: Clavicle unstable in vertical and horizontal planes
Type 4: Rupture off all supporting structures, clavicle displaced in or through trapezius muscles Comments: -
Type 5: Rupture of all supporting structures Comments: Most severe form of type 3 injury
Type 6: Rupture of all supporting structures Comments: Very uncommon

Shoulder pain - Pain over the top of the shoulder, often described as a deep ache.
Pain with reaching overhead, across body and pain when lying on side.
Tenderness to touch the top of the shoulder over the ACJ
Pain with putting weight though affected arm
Often ‘clicking’ with shoulder movements
With more significant injuries you can notice a ‘step deformity’ when looking in the mirror. This is where the clavicle (collar bone) sits slightly proud to the acromion of the shoulder.