AcromioClavicular (ACJ) Joint Injuries

How Does The AC Joint Get Injured?

Some injuries to the AC Joint result from a sudden trauma. Common mechanisms of this type of injury are falling onto your hand, or onto the outside tip of your shoulder. This can result in a sprain of the AC Joint, or a separation of the joint with disruption of the ligaments. If there ligaments have been ruptured in your accident, this will present by a bump over your AC Joint. To learn more about the different types of AC Joint injuries, check out our blog by clicking here

Other injuries to the AC Joint result from either old injuries to the joint, or weakness from the scapula muscles. The clavicle is the only bony that connects the shoulder blade to the body. Consequently, the shoulder relies on muscle stability around the shoulder blade to support the ACJ. If there are long periods of shoulder blade weakness, this can cause irritation of the AC Joint.

Common Presentations

Acute pain from the AC Joint usually presents with localised tenderness at the top of the shoulder. In some cases there is a bump on the top of the shoulder. This pain is usually superficial, like you can touch it on the surface. At other times the AC Joint can refer pain to different areas of the body. this can be up towards your neck, along the top of your shoulder blade, or down the back of your arm.

Your physio will help diagnose whether you have an AC Joint injury by asking you some questions about your pain, and what makes it better or worse. People with an AC Joint Injury commonly have increased pain when the arm is across in front of their body, or they have reached overhead at the end of their available range. Your physio will also carry out some clinical tests to diagnose whether your pain is originating from your AC Joint. These will include tests such as palpation, horizontal flexion / scarf test, Paxinos sign, or Piano key test.