The scapula attaches directly to the clavicle (collar bone) through the acromioclavicular ligament. Together, the scapula and clavicle form the shoulder girdle. The structure of the shoulder girdle allows for a wide range of scapular movement.
The scapula sort of floats around the upper back area. It can move up and down, rotate medially and laterally, protract and retract.
The major muscle insertions that affect these movements are the trapezius, latissimus dorsi, serratus anterior, and the rhomboid muscles.
The scapula is the origin (at least in part) of the majority of muscles that affect articulation at the glenohumeral joint. These muscles include the biceps brachii, triceps brachii, deltoids, and all 4 rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis).