The Hip - book
Home » Muscles Tendons » Acromioclavicular Joint

Acromioclavicular Joint


  • AC joint is situated between the clavicle and acromion;
  • acromion has two ossification centers which fuse at age 22 yrs;
  • it permits motion in three planes:
    • AP gliding of acromion during protraction & retraction of scapula;
    • tilting of acromion during abduction & adduction of arm;
    • rotation of the clavicle;
    • rotation occurs during abduction & adduction of shoulder.


  • innervation: provided by the suprascapular and lateral pectoral nerves
  • ref: The suprascapular nerve and its articular branch to the acromioclavicular joint: an anatomic study
  •  joint is reinforced by two sets of ligaments:
    • AC ligament
      • directed horizontally, and functionally the AC joints control horizontal stability;
      • palpable shallow depression between end of clavicle & acromion;
      • superior AC lig is most important ligament in stabilizing AC joint for normal daily activities;
    • coracoclavicular ligaments:
      • stronger, vertically directed contains conoid and trapezoid ligaments help to control vertical stability;
      • coracoclavicular lig are suspensory ligaments of upper limb;
      • conoid:
        • is the most important ligament for support of the joint against significant injuries and superior displacement;
        • cone shaped which extends between the conoid tubercle on the posterior clavicle and the base of the coracoid;
      • trapezoid:
        • resists AC joint compression;
        • begins anteriorly and laterally to the conoid ligament on the clavicle and inserts on the coracoid process;
      • reference: Biomechanical study of the ligamentous system of the acromioclavicular joint.
    •     - Sternoclavicular joint:

Management of Specific Injuries