It is composed of parallel fibers, which interlace with the aponeuroses of the trapezius and deltoideus; below, it is in contact with the articular disk when this is present.

It is in relation, above, in rare cases with the articular disk; below, with the tendon of the supraspinatus The coracoacromial ligament is a strong triangular band, extending between the coracoid process and the acromion.

It is attached, by its apex, to the summit of the acromion just in front of the articular surface for the clavicle; and by its broad base to the whole length of the lateral border of the coracoid process.

When the pectoralis minor is inserted, as occasionally is the case, into the capsule of the shoulder-joint instead of into the coracoid process, it passes between these two bands, and the intervening portion of the ligament is then deficient.

[4] It does not properly belong to the acromioclavicular joint articulation, but is usually described with it, since it forms a most efficient means of retaining the clavicle in contact with the acromion.

It may be caused by a prior trauma (secondary osteoarthritis) or occur as a chronic degenerative disorder often co-existing with subacromial impingement.