The AC ligament is the primary restraint against horizontal (anteroposterior) clavicular displacement at the AC joint, complementing the CC ligaments which provide vertical stability. In Grade I-II AC separations, the CC ligaments are intact and only the AC ligament is sprained or torn. In Grade III the CC ligaments are also disrupted. The AC ligament is repaired or reconstructed alongside the CC ligaments in surgical AC joint stabilisation.
| Origin | Lateral clavicle (superior and inferior surfaces) |
|---|---|
| Insertion | Acromion (medial border — superior and inferior aspects) |
| Actions | Horizontal stability of the AC joint; resists anteroposterior clavicular displacement; acts with the CC ligaments for overall AC joint stability |
|---|
Horizontal instability of the AC joint (positive horizontal compression test — pushing the clavicle posteriorly reproduces pain and instability) indicates AC ligament insufficiency. In AC joint reconstruction, the AC ligament is repaired using the residual ligament tissue with suture augmentation alongside the CC ligament reconstruction graft.
Horizontal clavicular instability from AC ligament disruption in Grade I-III separations managed conservatively or with combined AC and CC ligament reconstruction.
