Acromioclavicular joint

Dr Jeremy Jones et al.

The acromioclavicular (AC) joint is a plane synovial joint of the pectoral girdle.

The AC joint is between the small facets of the convex distal clavicle and flat medial acromion. The articular surfaces are lined with hyaline cartilage 4. A wedge-shaped articular disc made from fibrocartilage separates the two articular surfaces, but its function is unknown 2, 6

A weak, synovium-lined joint capsule is attached to the articular margins and is reinforced superiorly by blended fibres of the trapezius muscle 6.


Static stabilisation is provided by: 

  • coracoclavicular ligament: main stabliser 2, 5
  • superior and inferior acromioclavicular ligaments: reinforce the relatively weak joint capsule 5

Dynamic stabilisation is also provided by the deltoid and trapezius muscles, with the superior AC ligament blending with these muscles' aponeuroses. 

Upper limb anatomy
Share article

Article Information

rID: 10208
Section: Anatomy
Tag: cases
Synonyms or Alternate Spellings:
  • ACJ
  • Acromioclavicular joint
  • Acromio-clavicular joint (ACJ)
  • AC joint

Support Radiopaedia and see fewer ads

Cases and Figures

  • Drag
    Bones and ligamen...
    Figure 1
    Drag here to reorder.
  • Drag
    Case 1: normal acromioclavicular joint
    Drag here to reorder.
  • Drag
    Supraspinatus tear
    Case 2: AC joint osteoarthritis
    Drag here to reorder.
  • Updating… Please wait.

    Alert accept

    Error Unable to process the form. Check for errors and try again.

    Alert accept Thank you for updating your details.