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Acromioclavicular Joint

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  • Planar diarthrodial joint
  • Formed by the junction of the anteromedial acromion and lateral clavicle
  • Clavicle has 3 ossification centers[1]
    • Beginning at 5 to 6 weeks’ gestation
    • Clavicular ossification often is not complete until 25 years of life
  • Acromion has 4 ossification centers[2]
    • 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[3]
    • 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[4]
  • 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




  • Blood Supply
    • Suprascapular Artery
    • Thoracoacromial Artery


Clinical Significance

See Also

  1. Ogata, S, Uhthoff, HK. The early development and ossification of the human clavicle—an embryologic study. Acta Orthop Scand. 1990;61(4):330-334.
  2. Warner, JJP, Beim, GM, Higgins, L. The treatment of symptomatic os acromiale. J Bone Joint Surg Am. 1998;80(9):1320-1326.
  3. 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.
  4. 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:
21 February 2020 21:47:58