Definition

By: Gregory R. Waryasz, MD

The rhomboid muscle of the musculoskeletal system is characterized by the major and minor components.

It is part of the deep posterior axioappendicular muscles.  It consists of skeletal muscle fibers.

Its unique structural features include its major and minor components that are not always clearly separate from each other.  The rhomboids appear as an oblique equilateral parallelogram.  The rhomboid major is thin, flat, and wide. The rhomboid minor is thicker and more superior than the rhomboid major.

The origin of the rhomboid major is at the spinous processes of T2 to T5. The origin of the rhomboid minor is the nuchal ligament and spinous processes of C7 to T1.

The insertion of the rhomboid major is the medial border of the scapula from the level of the spine to the inferior angle. The insertion of the rhomboid minor is the smooth triangular area at the medial scapular spine.

The blood supply is from the dorsal scapular artery and venous drainage is from the accompanying veins.

The innervation is from the dorsal scapular nerve.

The rhomboid muscle as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.

The function of the rhomboids is to retract the scapula and rotate it to depress the glenoid cavity.  The rhomboids also help to fix the scapula to the thoracic wall.  The rhomboid major adducts the scapula and elevates the medial border. The glenoid cavity also rotates inferiorly due to the inferior fibers of the rhomboid major. The rhomboid minor helps to adduct and elevate the scapula by working synergistically with trapezius, levator scapula, latissimus dorsi, and rhomboid major.  Activities like using a sledge hammer to drive in a stake into the ground rely on the rhomboids to forcibly lower raised upper limbs.

Common diseases include muscle strain and injury to the dorsal scapular nerve.

Injury to the dorsal scapular nerve can result in unilateral paralysis of the rhomboids.  The scapula on the affected side can migrate more lateral than the normal side.

Commonly used diagnostic procedures include clinical history, physical exam, and MRI.

It is usually treated with physical therapy and NSAIDs for muscle strain.

References

Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.

Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.

Wheeless’ Textbook of Orthopaedics: Rhomboids (http://www.wheelessonline.com/ortho/rhomboids)