Rhomboideus major is a quadrilateral sheet of muscle, which lies with rhomboideus minor and levator scapulae in the posterior neck and chest wall, superficial to the long back muscles and deep to trapezius, except at the Triangle of auscultation.

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.

Nerve Supply
The dorsal scapular nerve, derived from C4 and C5, supplies rhomboideus major.

Action
Together with rhomboideus minor, levator scapulae and pectoralis minor it medial rotates the scapula; with rhomboideus minor and trapezius it retracts the scapula.   It also acts to stabilize the scapula when other muscle groups are active.

For more information on the shoulder see 'The Interactive Shoulder'.