Acromioclavicular joint

• Surrounded by a synovial membrane, the AC joint is supported by the AC ligament and the coracoclavicular ligament, which suspend the scapula from the clavicle.

• A synovial disc is present between the clavicle and the acromion that disappears by the fourth decade of life.

• Divided into two separate bands, the superior and inferior portions of the AC ligament function to maintain continuity between the articulating surfaces of the acromion and clavicle.

• With much of its restraint in the horizontal plane, this ligament maintains stability by preventing the clavicle from riding up and over the acromion process.