Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Acromioclavicular joint injuries ("separated" shoulder)

Scott M Koehler, MD
Section Editor
Karl B Fields, MD
Deputy Editor
Jonathan Grayzel, MD, FAAEM


The acromioclavicular (AC) joint is situated at the distal end of the clavicle forming an articulation with the acromion of the scapula (picture 1). The AC joint complex is strong, but its location makes it vulnerable to injury from direct trauma. Injuries to the AC joint are classified according to the position of the clavicle with respect to the acromion and coracoid. Treatment is based upon the extent of injury. AC joint injuries are sometimes referred to as sprains or a "separated" shoulder.

The evaluation and management of AC injuries will be reviewed here. Chronic and atraumatic conditions of the acromioclavicular joint, as well as a general approach to the patient with shoulder pain and discussions of other specific shoulder injuries are found separately. (See "Acromioclavicular joint disorders" and "Evaluation of the patient with shoulder complaints" and "Glenohumeral osteoarthritis" and "Multidirectional instability of the shoulder" and "Rotator cuff tendinopathy".)


A more complete discussion of shoulder anatomy and biomechanics is found separately. The structure and function of the acromioclavicular (AC) joint is described below. (See "Evaluation of the patient with shoulder complaints", section on 'Anatomy and biomechanics'.)

The AC joint is supported by ligaments that span its anterior, superior, posterior, and inferior aspects (picture 1). These ligaments also envelop the distal 1 to 2 cm of the clavicle. In addition to the AC ligaments, the distal clavicle is held in alignment with the acromion by the strong coracoclavicular (CC) ligaments. These ligaments consist of the conoid ligament medially and the trapezoid ligament laterally. The AC joint itself has a cartilaginous disk and synovial membrane.

Joint motion is limited, but the clavicle can rotate a few degrees, and small amounts of translation and slight angulation are possible. The clavicle and scapula tend to move in unison, and investigators have shown fully preserved shoulder range of motion (ROM) with fusion of the AC joint [1]. Anatomic drawings of the shoulder are provided (figure 1 and figure 2 and figure 3).

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Dec 02, 2016.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Renfree KJ, Wright TW. Anatomy and biomechanics of the acromioclavicular and sternoclavicular joints. Clin Sports Med 2003; 22:219.
  2. Lemos MJ. The evaluation and treatment of the injured acromioclavicular joint in athletes. Am J Sports Med 1998; 26:137.
  3. Rockwood, CA, Williams, et al. Disorders of the AC join. In: The Shoulder, WB Saunders, Philadelphia 1998. Vol Volume 1, p.483.
  4. Pallis M, Cameron KL, Svoboda SJ, Owens BD. Epidemiology of acromioclavicular joint injury in young athletes. Am J Sports Med 2012; 40:2072.
  5. Hibberd EE, Kerr ZY, Roos KG, et al. Epidemiology of Acromioclavicular Joint Sprains in 25 National Collegiate Athletic Association Sports: 2009-2010 to 2014-2015 Academic Years. Am J Sports Med 2016; 44:2667.
  6. Vanarthos WJ, Ekman EF, Bohrer SP. Radiographic diagnosis of acromioclavicular joint separation without weight bearing: importance of internal rotation of the arm. AJR Am J Roentgenol 1994; 162:120.
  7. Buss DD, Watts JD. Acromioclavicular injuries in the throwing athlete. Clin Sports Med 2003; 22:327.
  8. Bossart PJ, Joyce SM, Manaster BJ, Packer SM. Lack of efficacy of 'weighted' radiographs in diagnosing acute acromioclavicular separation. Ann Emerg Med 1988; 17:20.
  9. Peetrons P, Bédard JP. Acromioclavicular joint injury: enhanced technique of examination with dynamic maneuver. J Clin Ultrasound 2007; 35:262.
  10. Tamaoki MJ, Belloti JC, Lenza M, et al. Surgical versus conservative interventions for treating acromioclavicular dislocation of the shoulder in adults. Cochrane Database Syst Rev 2010; :CD007429.
  11. Reid D, Polson K, Johnson L. Acromioclavicular joint separations grades I-III: a review of the literature and development of best practice guidelines. Sports Med 2012; 42:681.
  12. Cote MP, Wojcik KE, Gomlinski G, Mazzocca AD. Rehabilitation of acromioclavicular joint separations: operative and nonoperative considerations. Clin Sports Med 2010; 29:213.
  13. Montellese P, Dancy T. The acromioclavicular joint. Prim Care 2004; 31:857.
  14. Bradley JP, Elkousy H. Decision making: operative versus nonoperative treatment of acromioclavicular joint injuries. Clin Sports Med 2003; 22:277.
  15. Spencer EE Jr. Treatment of grade III acromioclavicular joint injuries: a systematic review. Clin Orthop Relat Res 2007; 455:38.
  16. Phillips AM, Smart C, Groom AF. Acromioclavicular dislocation. Conservative or surgical therapy. Clin Orthop Relat Res 1998; :10.
  17. Wojtys EM, Nelson G. Conservative treatment of Grade III acromioclavicular dislocations. Clin Orthop Relat Res 1991; :112.
  18. Press J, Zuckerman JD, Gallagher M, Cuomo F. Treatment of grade III acromioclavicular separations. Operative versus nonoperative management. Bull Hosp Jt Dis 1997; 56:77.
  19. Schlegel TF, Burks RT, Marcus RL, Dunn HK. A prospective evaluation of untreated acute grade III acromioclavicular separations. Am J Sports Med 2001; 29:699.
  20. Bannister GC, Wallace WA, Stableforth PG, Hutson MA. The management of acute acromioclavicular dislocation. A randomised prospective controlled trial. J Bone Joint Surg Br 1989; 71:848.
  21. Larsen E, Bjerg-Nielsen A, Christensen P. Conservative or surgical treatment of acromioclavicular dislocation. A prospective, controlled, randomized study. J Bone Joint Surg Am 1986; 68:552.