Proximal Attachment
It arises by tendinous fibers from the spinous processes and intervening supraspinous ligaments of T2 to T5.

Distal Attachment
It passes obliquely infero-laterally with most fibers ending in a tendinous band attaching to the medial border of the scapula by a thin membrane between the base of the spine and inferior angle; some muscular fibers may attach directly to the scapula.