Full Acromioclavicular Ligament Description
[Continued from above] . . . parallel fibers, which are interlaced with the aponeuroses (or tendons) of the trapezius and deltoid muscles. If the articular disk is present, then the bottom edge of the superior acromioclavicular ligament is attached there. This ligament gives the acromioclavicular joint its horizontal stability.
The inferior acromioclavicular ligament is thinner than the superior; it covers the lower part of the joint, and is attached to the two bones along their adjoining surfaces. If the articular disk is present, then the top edge of this ligament connects to the disk; its lower edge is in relation with the tendon of the supraspinatus muscle (a small muscle of the upper arm).