Acromioclavicular joint injuries


The acromioclavicular (AC) joint is a diarthrodial joint that anchors the clavicle to the scapula and shoulder girdle, it helps distribute forces from the upper extremities to the axial skeleton.[1-4] Static stability at the AC-joint is achieved via the AC-ligaments, capsule, and coracoclavicular (CC) ligaments, whilst dynamic stability is provided by the Deltoid and Trapezius muscles.[1-5] As the AC-joint lies relatively subcutaneously there is little protection from soft tissues, and as such is prone to injury; specifically within contact sports,[2,5-6] i.e. via trauma.  It is reported that AC-joint injuries comprise 9-12% of all injuries to the shoulder girdle,[2-4,6] with males in their 20’s having the highest rate of injury.[2-3,6]


As with most traumatic injuries, the AC-joint can be injured by direct or indirect trauma. Direct trauma to the AC-joint is caused when a person lands on the point of their shoulder, as seen in multiple collision sports; which forces the acromion inferiorly and medially.[2-4] Indirect trauma is caused when a person falls on an outstretched hand (FOOSH), and the force is transmitted up the arm forcing the humeral head into the acromion.[1-3] Whether the injury was cause by direct or indirect trauma matters not, the classification is based on structural involvement and displacement present; therefore higher levels of force involved will lead to a higher classification.

There are many methods of classifying ligament or muscle injuries throughout the literature, [7] with the research surrounding AC-joints’ being no different. The most commonly recognized classification is known as the Rockwood classification[1,4] (Table 1). The Rockwood grading system is based on physical and radiographic findings,[1-6] whereas in the clinic it would be down to the level of visual displacement and painful areas upon palpation. Throughout the classifications, the higher classifications of injury are shown to have greater ligamentous involvement and a greater displacement present.

Table 1: AC-joint injury – Rockwood classifications[1,4]

Best treatment for injuries I, II, and IV-VI has been clearly established within the literature.[1-6] Type I and II injuries are treated conservatively with treatment commencing as comfort allows, as for type IV-VI injuries the literature states that open reduction and internal fixation with ligament repair/reconstruction is the treatment which provides best prognosis. However, these authors all agree that type III injuries must be taken on a case-by-case basis. Current trends exist in the literature to show that conservative management provides an earlier return to work and sport[4] with Bontempo and Mazzocca[3] stating that: at a 2 year follow up, non-operatively versus operatively treated type III injuries had no difference in strength after 2 years. That being said Bannister et al. (1989) as cited by Lemos[1] state that those with a displacement greater than 2cm did better with operative intervention, while Bontempo and Mazzocca[3] go on to say that surgery may be indicated in those whose symptoms persist after a full course of rehabilitation.

The primary aim of rehabilitation for an AC-joint injury is to restore pain free Range of Motion (ROM), how quickly this happens will depend on the type of injury and whether this is the first or a subsequent injury. Rehabilitation programs involve modification of the patients’ work and daily activities in the initial phase before gradually introducing and progressing exercises.[1-6] For non-operative treatment, Bontempo and Mazzocca[3] proposed an algorithm (Figure 1), which showed that athletes should go through a 3-month functional rehab program before surgery is considered.


Figure 1: Non-Operative treatment algorithm proposed by Bontempo and Mazzocca[3]

Case Study

As an example, we will take a patient with a Grade II injury: they have a decreased ROM across all shoulder movements, an associated decrease in strength, with pain and laxity present. After assessment the patient would be advised to continue with the P.O.L.I.C.E (Protection, Optimal Loading, Ice, Compression, Elevation) principle[8] and to reduce the amount of overhead and heavy work conducted,[1-6] whilst avoiding competitive sport and heavy lifting until cleared.[6] Initially the patient would be placed in a broad arm sling and advised to wear it regularly over the first 1-2 weeks; this advice would be accompanied by passive ROM exercises to prevent the shoulder from becoming stiff whilst in the sling.


When pain starts to subside, patients would be advised to wean themselves out of the sling by trying to use their arm for light daily activities. Whilst increasing their ROM exercises, and to begin replacing passive ROM with active assisted exercises and isometric holds throughout range;[2,5] this would include hold-relax proprioceptive neuromuscular facilitation (PNF) patterns for the upper limb.[9]

Once full pain-free ROM has been achieved the patient would begin an upper limb rehabilitation program to strengthen the AC-joint and surrounding structures; to provide additional pain relief during the early stages of the rehab program the AC-joint may be taped.[5-6,10-11] Strength exercises primarily focus on the trapezius and deltoid muscles (table 2), while elements of neuromuscular control (NMC)[5,12-13] would be introduced to strengthen the rotator cuff and additional musculature about the scapulae (table 3).

Table 2: examples of strength rehabilitation exercises

Table 3: examples of NMC rehabilitation exercises


To summarize, the AC-joint is a very superficial joint prone to traumatic injuries, for example in contact sports, the higher the levels of force in the injury will generally lead to a higher classification of injury; with it comprising 9-12% of all injuries to the shoulder girdle,[2-4, 6] and males in their 20’s having the highest rate of injury.[2, 4, 6]. The primary method for classifying AC-joint injuries involves both physical and radiographic findings, however in the clinic the grading will rely on the level of visual displacement and painful areas on palpation with Higher levels of force generally leading to a higher classification of injury. The primary aim of rehabilitation for an AC-joint injury is to restore pain free ROM, how quickly this happens will depend on the type of injury and whether this is the first or a subsequent injury. Although type III injuries provide an area of contention within the research, the majority of rehabilitation programs follow a conservative approach similar to that of type I and II injuries. For an injury to the AC-joint, a rehabilitation program will include: modification of the patients’ work and daily activities in the initial phase, before gradually introducing and progressing exercises. This along with NMC and dynamic stabilising exercises would assist in not just rehabilitating the primary injury but assist in preventing further injuries to the AC-joint.




  1. Lemos, M.J., 1998. The evaluation and treatment of the inured acromioclaviculae joint in athletes. The American Journal of Sports Medicine, 26(1), pp. 137-144.
  2. White, B., Epstein, D., Sanders, S. and Rokito, A., 2008. Acute acromioclavicular injuries in adults. Orthopaedics, 31(12), pp. 1219-1226.
  3. Bontempo, N.A. and Mazzocca, A.D., 2010. Biomechanics and treatment of acromioclavicular and sternoclavicular joint injuries. British Journal of Sports Medicine, 44(5), pp. 361-369.
  4. Wright, A.P., MacLeod, I.A.R. and Talwalker, S.C., 2010. Disorders of the acromioclavicular joint and distal clavicle. Orthopaedics and Trauma, 25(1), pp. 30-36.
  5. Brukner, P. and Khan, K. 2013. Clinical sports medicine. 4th Australia: McGraw-Hill Education.
  6. Fraser-Moodie, J.A., Shortt, N.L. and Robinson, C.M., 2008. Injuries to the acromioclavicular joint. The Journal of Bone & Joint Surgery, 90(6), pp. 697-707.
  7. Mueller-Wohlfahrt, H.W., Haensel, L., Mithoefer, K., Ekstrand, J., English, B., McNally, S., Orchard, J., Van Dijk, C.N., Kerkhoffs, G.M., Schmasch, P., Blottner, D., Swaerd, L., Goedhart, E. and Ueblacker, P., 2013. Terminology and classification of muscle injuries in sport: The Munich consensus statement. British Journal of Sports Medicine, 47(6), pp. 342-350.
  8. Bleakley, C.M., Glasgow, P. and MacAuley, D.C., 2012. PRICE needs updating, should we call the POLICE? British Journal of Sports Medicine, 46(4), pp. 220-221.
  9. Kwak, D.H. and Ryu, Y.U., 2015. Applying proprioceptive neuromuscular facilitation stretching: optimal contraction intensity to attain the maximum increase in range of motion in young males. Journal of Physical Therapy Science, 27(7), pp. 2129-2132.
  10. Shamus, J.L. and Shamus, E.C., 1997. A taping technique for the treatment of acromioclavicular joint sprains: a case study. Journal of Orthopaedic and Sports Physical Therapy, 25(6), pp. 390-394.
  11. Kneeshaw, D., 2002. Shoulder taping in the clinical setting. Journal of Bodywork and Movement Therapies, 6(1), pp. 2-8.
  12. Gutierrez, G.M., Kaminski, T.W. and Douex, A.T., 2009. Neuromuscular control and ankle instability. PM & R: The Journal of Injury, Function, and Rehabilitation, 1(4), pp. 359-365.
  13. Herrington, L., Myer, G. and Horsley, I. 2013. Task based rehabilitation protocol for elite athletes following anterior cruciate ligament reconstruction: a clinical commentary. Physical Therapy in Sport, 14(4), 188-198.

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