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Acromioclavicular Joint Injury

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The Acromioclavicular (AC) joint – which may be coined the ‘tip’ of the shoulder, is formed by the lateral end of the collar bone (Clavicle) and part of the shoulder blade known as the Acromion. This joint assists with movement of the shoulder blade on the thorax and maximises shoulder range of movement and stability. Like all synovial joints it has a joint capsule and ligaments (Acromioclavicular, Coracoacromial and Coracoclavicular) in close proximity which provide stability. Also, the Trapezius and Deltoid muscles are suggested to provide additional stability when the arm shoulder is in motion (Kim, Blank & Strauss, 2014).

Signs & Symptoms

  • Pain on the top of the shoulder which may radiate into the neck and upper arm.
  • Symptoms aggravated by heavy lifting, overhead and across body movements.
  • Swelling/bruising.
  • Loss of shoulder movement.
  • A visible abnormality on the tip of the shoulder – commonly referred to as a ‘step’ deformity, indicating displacement or separation of the AC joint (Culp & Romani, 2006).


The most common mechanisms in which AC joint injuries occur is from a fall onto an outstretched hand or elbow, a direct blow or falling onto the point of the shoulder. AC joint injuries are commonly seen in contact sports such as football, rugby & hockey, and also cycling, skiing/snowboarding and road traffic accidents (Johansen et al., 2011).


AC joint injuries make up approximately 9% of all shoulder injuries (Gorbarty, Hsu & Gee, 2017). The degree of injury to the AC joint can be from a mild ligament sprain to complete ligament tear resulting in ‘separations of the AC joint’ or dislocations. Specific to athletes, separation of the joint is seen in 40% of shoulder girdle injuries.

Assessment & Diagnosis

Your Physiotherapist will take a detailed history to understand how the injury occurred and what your symptoms are. Following this, a comprehensive physical assessment will be completed to establish your function and test specific structures to assist with accurate diagnosis so that the most appropriate and effective treatment can begin straight away.


Gorbarty, Hsu & Gee (2017) outline the Rockwood classification for AC joint injuries which is a grading system used to establish the degree of damage, the structures involved and to inform treatment & management (Rockwood & Green, 1996):


Grade I – Sprain of the Acromioclavicular ligament only, remains stable.

Grade II – Acromioclavicular ligament rupture, unstable with direct pressure. Also referred to as a subluxation in which the joint is displaced during the injury but returns to its anatomical position.

Grade III – Acromioclavicular and Coracoclavicular ligament rupture – dislocation of the joint. The ‘step deformity’ is usually observed and the lateral clavicle is unstable horizontally and vertically.


Grade IV – the distal portion of the clavicle is displaced posteriorly into the trapezius muscle with the deformity usually being observable.

Grade V – A more severe Grade III, the joint is significantly more separated with superior translation of the distal clavicle and the shoulder blade has dropped down.

Grade VI – Damage to an even greater extent in which the collar bone is displaced forwards and down, dropping below the height of the shoulder. This will usually occur with severe trauma only.


In cases where function is relatively well maintained, there are several physical tests that will help establish the grade of the injury – usually I-III. However, in more cases an X-ray is utilised to assist with grading and to guide ongoing treatment and management.


Your Physiotherapist will work with you to develop a set of individualised goals so help direct your treatment and facilitate optimal recovery with a successful return to normal activity. We value regular re-assessment to ensure you are making progress and to allow adjustments in your treatment to be made.


In the immediate period following injury, the POLICE protocol should be adopted – protection, optimal loading, ice, compression, and elevation alongside a referral within 48 hours if deemed appropriate. A sling/brace is advised to immobilise the shoulder, this can be used in tandem with taping to provide the joint with additional support. Elevating the shoulder to a comfortable height is also suggested when resting. A sling can be used until symptoms diminish and function returns. For grade I – III injuries, patients typically return to normal function at 2-4, 4-6 and 6-12 weeks, respectively (Culp & Romani 2006). Your Physiotherapist will help explain the injury and what structures are involved so that you can understand your symptoms and help support your own recovery. As you recover, we provide ongoing guidance so that you can effectively return to your normal activities whilst minimising the likelihood of future complications.


Your Physiotherapist can assist with pain management and design a personalised and progressive rehabilitation programme, helping to restore full movement and function, increase strength and eventually support a return to sporting activity where appropriate. In the early stages, exercises will be focus on improving range of motion whilst keeping the articulating muscles active – preventing weakening whilst the shoulder is less mobile. As your movement returns, the exercises will be progressed to more challenging movements to develop strength through full range. Lastly, sports- or activity-specific exercise will be implemented for a full return to normal activity.

Escalation of Treatment

In severe and traumatic cases – grade IV-VI, there is a high likelihood that surgical intervention will be required as the preferred treatment approach (Johansen et al., 2011). Surgery will restore normal anatomy and stability to the joint. Post-surgical management is very similar to that of lower grade injuries beginning with increasing range of motion before moving on to strengthening exercises and a graded exposure to higher level exercise for return to baseline function.


Culp, L. B., & Romani, W. A. (2006). Physical therapist examination, evaluation, and intervention following the surgical reconstruction of a grade III acromioclavicular joint separation. Physical therapy86(6), 857-869.


Gorbaty, J. D., Hsu, J. E., & Gee, A. O. (2017). Classifications in brief: Rockwood classification of acromioclavicular joint separations.


Johansen, J. A., Grutter, P. W., McFarland, E. G., & Petersen, S. A. (2011). Acromioclavicular joint injuries: indications for treatment and treatment options. Journal of shoulder and elbow surgery20(2), S70-S82.


Kim, S., Blank, A., & Strauss, E. (2014). Management of Type 3 Acromioclavicular Joint Dislocations. Bulletin of the Hospital for Joint Diseases72(1).


Rockwood, C. A., & Green, D. P. (1996). Fractures in adults. In Fractures in adults.

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