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Acromioclavicular Joint

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Illustration of the acromioclavicular joint[1]
  • Planar diarthrodial joint
  • Formed by the junction of the anteromedial acromion and lateral clavicle
  • Clavicle has 3 ossification centers[2]
    • Beginning at 5 to 6 weeks’ gestation
    • Clavicular ossification often is not complete until 25 years of life
  • Acromion has 4 ossification centers[3]
    • Preacromion, meta-acromion, and mesoacromion fusing together by 18 years of life
  • A fibrocartilaginous disk cushions the joint
    • The disk is composed of 75% water, 20% collagen (90% of which is type I, with minor contributions from types II, III, and IV), and 5% proteoglycans, elastin, and other cells[4]
    • Degeneration of the intra-articular meniscus is thought to contribute to osteoarthritis
    • Commonly observed in patients over the age of 50 years, begins as early as the second decade of life[5]
  • Acromioclavicular Ligament
    • Resist 50% of anterior and 90% of posterior displacement
  • Coracoclavicular Ligaments
    • Primary: resist superior and axial translation
    • Secondary: resist anterior and posterior translation in the absence of AC ligaments


  • Axial rotation and anteroposterior movement of shoulder


  • Blood Supply
    • Suprascapular Artery
    • Thoracoacromial Artery


Clinical Significance

See Also

  1. Image courtesy of teachmeanatomy, "The Acromioclavicular Joint"
  2. Ogata, S, Uhthoff, HK. The early development and ossification of the human clavicle—an embryologic study. Acta Orthop Scand. 1990;61(4):330-334.
  3. Warner, JJP, Beim, GM, Higgins, L. The treatment of symptomatic os acromiale. J Bone Joint Surg Am. 1998;80(9):1320-1326.
  4. Brys, P, Geusens, E Scapular, clavicular, acromioclavicular and sternoclavicular joint injuries. In: Vanhoenacker, FN, Maas, M, Gielen, JL, eds. Imaging of Orthopedic Sports Injuries. Berlin, Germany: Springer-Verlag; 2007:169-182.
  5. DePalma, AF . The role of the discs of the sternoclavicular and acromioclavicular joints. Clin Orthop Relat Res. 1959;13:7-12.
Created by:
John Kiel on 21 February 2020 20:36:07
Last edited:
11 September 2022 07:03:26