Acromioclavicular (AC) Joint Injury

What is the AC Joint?

The AC joint is one of 4 joints that comprise the shoulder complex. It attaches the scapula (shoulder blade) to the clavicle (collarbone) and serves as a point of articulation that allows our arm to attach to the rest of our body. The AC joint is held together with muscles (deltoid, trapezium) and ligaments (acromioclavicular [AC] and coracoclavicular [CC]) that prevent dislocation of the joint. You can spot it on yourself if you look towards either shoulder, and can look and feel for the ‘boniest’ part before the upper arm starts.

Mechanisms of an AC Joint injury:

The most common mechanism of AC joint injury is direct trauma to the outside of the shoulder when the arm is tucked in by the side of the body. This can occur when falling on the tip of your shoulder or direct blow to your shoulder like a “hip and shoulder” whilst playing sport or falling off a bike while the hand is still on the handlebar. They are most common in overhead and collision sports such as AFL and Rugby.

What are signs for you to look out for?

• Pain over the AC joint. There can be some associated referred pain in the shoulder and upper trapezius muscle
• Pain during weight training activities such as chest press, push ups or shoulder press
• A visible deformity can also be seen by the naked eye in higher grade injuries of the AC joint

If you suspect an AC joint injury, our  team of Physiotherapists can help identify the severity of the injury.

X-rays may be recommended to help determine the degree of severity regarding the AC Joint injury. The grades of AC Joints are:

Grade I: Stretching of the ligaments but the fibres are intact

Grade II: Disruption (tearing) of the AC ligament and stretching of the CC ligament

Grade III: Disruption of AC & CC ligaments

Grade IV, V, VI are more severe gradings that involve disruption of ligaments and musculature of supporting structures.

*Grade I and II can be treated non-surgically, and typically respond very well to this type of treatment. If you present with a Grade III+, your physiotherapist may refer you to an orthopaedic surgeon for their opinion regarding surgical intervention.

How can physiotherapy help with your AC injury?

Physiotherapy is beneficial for both surgical and non-surgical treatment options. Your physiotherapist will initially focus on managing acute symptoms such as pain and regaining range of movement. Taping is a great way to assist with stability and avoid aggravating movements in the beginning. Once pain has reduced and range of motion returned, your physiotherapist will work to progressively strengthen your muscles around your scapula and shoulder.

When can you expect to return to sport after an AC injury?

• Grade l: 2-4 weeks
• Grade ll: 4-8 weeks
• Grade lll+: 12-16 weeks

The following timelines are guidelines only and the time will vary based on the severity of the injury and how adherent you are to your rehabilitation program. Your physio will perform relevant return to sport testing to help give you return to your given sport / activity safely. At Instinct Health we have access to various testing tools:

• A hand-held dynamometer to establish specific muscle group strength (Rotator cuff, deltoid, bicep)
• VALD Force Plates to measure upper body performance and the transfer of force across the shoulder griddle. (Athletic Shoulder (ASH) test, Maximum Push Up test)

If you’re suspicious of an AC joint injury, or any other type of injury to the shoulder, make contact with one of our physios so that they can give you a thorough assessment and put a strong plan in place for your return to sport, work or life!