AC Joint Injury
The acromio-clavicular (AC) joint is the joint formed between the clavicle (collarbone) and the acromion (the tip of the shoulder blade). You can feel it, if you put your hand on top of your shoulder, it is the bony bump about 4cms from the edge of the shoulder.
The AC joint is a link between the arm and the trunk and is the only bony join between the shoulder blade and the rest of the body. It helps transmit load from the arm to the trunk in pushing, pulling punching and resting on the arm.
How the AC joint is injured?
The AC joint is a quite common sporting injury especially in contact sports. It is usually injured by a fall directly onto the shoulder or a fall onto the arm or a tackle.
The ligaments that bind the clavicle to the acromion are firstly stretched, then torn. Depending on the severity of the injury the clavicle can tear away from the acromion causing a noticeable lump to appear on top of the shoul-der. The injury results in considerable pain, swelling and loss of shoulder movement.
The injury does heal, depending on the severity of the injury by itself or if complicated with surgical intervention. However many years later degenera-tion can cause the AC joint to become painful again.
Grading of an AC joint injury:
The most commonly used classification system recognises 6 severities of AC joint injury.
Grade I: A slight displacement of the joint. The acromioclavicular ligament may be stretched or partially torn. This is the most common type of injury to the AC Joint.
Grade 2: A partial dislocation of the joint in which there may be dome displacement that may not be obvious during a physical examination. The acromioclavicular ligament is completely torn, while the coracoclavicular ligaments remain intact.
Grade 3: A complete separation of the joint. The acromioclavicular ligament, the coracoclavicular ligaments and the capsule surrounding the joint are torn. Usually, the displacement is obvious on clinical exam. Without any ligament support, the shoulder falls under the weight of the arm and the clavicle is pushed up, causing a bump on the shoulder
Grades I-III are the most common. Grades IV-VI are uncommon and are usually a result of a very high-energy injury such as ones that might occur in a motor vehicle accident.
Treatment for an AC joint injury
Initial treatment may consist of:
- Support (a sling may be worn)
- Your doctor may prescribe anti-inflammatory medications or pain relief medication.
- Movement within the pain free range will help in maintaining mobility of the surrounding structures.
- Taping may be beneficial to support the position of the joint.
- Physiotherapy can use ultrasound and interferential currents, for pain and inflammation.
As pain settles:
- Load bearing exercises can be added to restore the normal function of the joint and surrounding muscles.
- Massage and mobility exercises may be incorporated to ensure normal function is achieved.
In severe cases where the clavicle is completely torn away from the acromion the joint may remain painful and unstable and require surgical fixation.
Returning to sport following an AC joint injury:
Return to sport is possible when you have no localized tenderness, and full range of pain free movement has been achieved. On initial return to sport you may feel more comfortable to use taping or to have some padding over the AC joint. Your physiotherapist will guide you on your return to sport and any precautions that need to be taken.
Examples of tasks you should be able to perform painfree are:
- Landing against a wall sideways with your shoulder.
- Landing against a wall onto an outstretched hand.
- Throwing and catching a ball in awkward positions.
- Completing one or more full contact training sessions.
- Seek treatment at an early stage
- Ensure your physiotherapist provides you with methods of self treatment and management.