The other major ligament is the coracoacromial ligament. Unlike the others, it is not a thickening of the joint capsule. It runs between the acromion and coracoid process of the scapula, forming the coraco-acromial arch. This structure overlies the shoulder joint, preventing superior displacement of the humeral head.ig 1.0 â The articulating surfaces of the shoulder joint. The shoulder joint is formed by the articulation of the head of the humerus with the glenoid cavity (or fossa) of the scapula. This gives rise to the alternate name for the shoulder joint â the glenohumeral joint.