Muscle · Upper limb
Rhomboid major: origin, insertion, action and innervation
The rhomboid major is a back muscle from the spines of T2-T5 to the medial border of the scapula. It retracts the scapula via the dorsal scapular nerve.
Quick answer
- Latin name
- Musculus rhomboideus major
- Origin
- Spinous processes of T2–T5 (thoracic vertebrae) and the supraspinous ligament
- Insertion
- Medial border of the scapula, from the root of the spine to the inferior angle
- Action
- Retracts the scapula; elevates its medial border and rotates it downward; holds it against the chest wall
- Innervation
- Dorsal scapular nerve (C4–C5)
- Blood supply
- Dorsal scapular artery (or the deep branch of the transverse cervical artery)
See it on the 3D body
The rhomboid major lit on the 3D back, as in the back quiz. Turn the body, peel the layers, tap any structure for its name.
The rhomboid major is a flat, four-sided muscle of the upper back that connects the thoracic spine (T2 to T5) to the inner edge of the shoulder blade. It pulls the scapula toward the spine (retraction) and helps hold it flat against the ribs.
Where it is
The rhomboid major lies between the two shoulder blades, in the second layer of back muscles. The trapezius covers it almost completely, so you only see it once the trapezius is lifted away. Under it lie the deeper back muscles and the ribs.
Its fibers run downward and outward, from the spine to the scapula, in parallel bands. Its shape, an oblique parallelogram, gives it its name: a rhomboid. Just above it, and often hard to separate from it, lies the smaller rhomboid minor, which comes from C7 and T1 and inserts at the level of the root of the scapular spine. Together the two rhomboids form a sheet that fills the gap between the spine and the medial border of the scapula.
The levator scapulae continues the same line higher up, from the neck vertebrae to the superior angle of the scapula. These three muscles (levator scapulae, rhomboid minor, rhomboid major) all attach along the medial border of the scapula, one above the other.
Origin and insertion
- Origin: the spinous processes of the second to fifth thoracic vertebrae (T2 to T5), and the supraspinous ligament that joins their tips. See the bones of the spine to locate them.
- Insertion: the medial border of the scapula, from the level of the root of the spine down to the inferior angle.
What it does
The rhomboid major moves the shoulder blade rather than the arm:
- Retraction: it pulls the scapula toward the spine, squeezing the shoulder blades together, as when you stand up straight, row a boat or pull open a heavy door.
- Elevation of the medial border: because its fibers slope upward toward the spine, it lifts the inner edge of the scapula slightly.
- Downward rotation: it turns the scapula so that the glenoid cavity tilts down. This helps lower a raised arm, together with the levator scapulae and the pectoralis minor.
- Holding the scapula in place: with the serratus anterior, it keeps the scapula pressed flat on the chest wall. The two muscles pull in opposite directions, the serratus anterior forward and around the ribs, the rhomboids back toward the spine, and their balance steadies the shoulder blade so the arm muscles have a firm base.
The middle fibers of the trapezius also retract the scapula, so the rhomboids and the trapezius work as a team in most pulling movements.
Innervation and blood supply
The rhomboid major is supplied by the dorsal scapular nerve (roots C4 and C5, mainly C5), which comes directly from the root of the brachial plexus. The nerve runs down along the medial border of the scapula, deep to the levator scapulae and the rhomboids, and also supplies the rhomboid minor and usually the levator scapulae.
Its blood comes from the dorsal scapular artery, which follows the nerve. In some people this vessel arises as the deep branch of the transverse cervical artery instead of directly from the subclavian artery.
How to remember it
- Rhomboid = rhombus shape, with fibers running down and out like a slanted ladder.
- Major is lower: the rhomboid major is below the rhomboid minor, and it is the larger of the two.
- Origins in order down the spine: levator scapulae (neck), rhomboid minor (C7–T1), rhomboid major (T2–T5).
- "Dorsal scapular nerve, dorsal scapular artery": the nerve and the artery share the name and run together.
- Squeeze your shoulder blades together: that is the rhomboids at work.
The muscles of the shoulder page groups it with the other muscles that steer the scapula.
Frequently asked questions
What is the main action of the rhomboid major?
Retraction of the scapula: it pulls the shoulder blade toward the spine. It also rotates the scapula downward and helps keep it flat against the ribs.
What is the difference between the rhomboid major and the rhomboid minor?
The rhomboid minor is smaller and higher, coming from C7 and T1. The rhomboid major is larger and lower, coming from T2 to T5. Both insert on the medial border of the scapula and share the same nerve and action.
Which nerve supplies the rhomboid major?
The dorsal scapular nerve, mainly from root C5 (with C4).
Can you see the rhomboid major from the surface?
Not really. It is covered by the trapezius, so you have to remove that muscle, in a dissection or in a 3D atlas, to see it.
