Muscle Review – Rhomboid Major and Minor

Muscle Review

Rhomboid Minor

Origin: Spinous processes of vertebrae C7-T1 and the inferior part of the nuchal ligament

Insertion: Medial (vertebral) border of the scapula at the root of the spine of the scapula

Action: Retracts and downwardly rotates the scapula

Innervation: Dorsal scapular nerve (C5)

Notes & Tips

The rhomboid minor is a small, rhomboid-shaped muscle located superior to the rhomboid major. It stabilizes the scapula by retracting and rotating it downward, counteracting protraction forces from the serratus anterior. Dysfunction or nerve injury can weaken scapular control, leading to excessive protraction or scapular winging. The rhomboid minor and major share the same innervation, so injury to the dorsal scapular nerve (C5) affects both.

Rhomboid Major

Origin: Spinous processes of vertebrae T2-T5

Insertion: Medial (vertebral) border of the scapula, from the root of the spine to the inferior angle of the scapula

Action: Retracts and downwardly rotates the scapula

Innervation: Dorsal scapular nerve (C5)

Notes & Tips

The rhomboid major, larger than rhomboid minor, lies directly beneath the trapezius and functions in scapular retraction and downward rotation. It works with the levator scapulae to oppose the upward rotation caused by the trapezius and serratus anterior. Weakness in the rhomboids can lead to poor scapular stability, affecting posture and shoulder mechanics. Since both rhomboids are innervated by the dorsal scapular nerve, dysfunction often presents as difficulty maintaining proper scapular positioning.

The rhomboid minor inserts at the root of the spine of the scapula, while the rhomboid major inserts along the medial border, extending from the root of the spine to the inferior angle. The root of the spine is located more superiorly than the inferior angle, making the rhomboid minor’s insertion higher. If you need a refresher on scapular landmarks, refer to Lesson 1: Bone Review for details on the structure and key features of the scapula.

The pectoralis minor and serratus anterior both protract the scapula, which opposes the retraction produced by the rhomboid muscles. Additionally, the serratus anterior also contributes to upward rotation, which counteracts the downward rotation produced by the rhomboids.

The dorsal scapular nerve (C5) innervates both the rhomboid minor and rhomboid major. This nerve arises from the brachial plexus, specifically from the C5 spinal root, and also innervates the levator scapulae.

Injury to the dorsal scapular nerve (C5) would weaken retraction and downward rotation of the scapula. This could result in excessive scapular protraction due to unopposed action of the serratus anterior and pectoralis minor, making the scapula appear more laterally displaced or “winged” at rest. Over time, this can contribute to postural imbalances and impaired shoulder mechanics.

The trapezius overlays the rhomboid major and rhomboid minor, so a massage therapist must work through or around the trapezius to effectively palpate the rhomboids. Since the trapezius is a broad, superficial muscle, applying firm but controlled pressure along the medial border of the scapula can help isolate the deeper rhomboids. Asking the client to retract their scapula against gentle resistance can help confirm activation of the rhomboids beneath the trapezius.

Downward rotation of the scapula occurs when the glenoid fossa moves downward and the inferior angle of the scapula moves medially and slightly upward toward the spine. This movement happens when lowering the arm from an overhead position or performing actions like a pull-up or reaching behind the back. Downward rotation is the opposite of upward rotation, where the glenoid fossa moves superiorly and the inferior angle moves laterally.

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