Definition
By: Gregory R. Waryasz, MD
The teres major muscle of the musculoskeletal system is characterized by it helping to form the triangular and the quadrangular space.
It is part of the scapulohumeral muscles. It consists of skeletal muscle fibers.
Its unique structural features include it being a thick and round muscle. When the arm is adducted against resistance, it forms a raised oval on the inferolateral third of the scapula.
The origin is the posterior inferior angle of the scapula.
The insertion is the medial lip of the humeral intertubercular groove.
The blood supply is from the subscapular and circumflex scapular arteries and venous drainage is from the accompanying veins.
The innervation is from the lower subscapular nerve.
The teres major 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 teres major is to adduct and medially rotate the arm. It works synergistically with the latissimus dorsi and the subscapularis. The teres major also helps to extend the arm from a flexed position. The humeral head is also stabilized in the glenoid by the teres major.
Common diseases include muscle strain and tears, but these are uncommon.
Commonly used diagnostic procedures include clinical history, physical exam, and MRI.
It is usually treated with physical therapy and NSAIDs.
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: Teres Major (http://www.wheelessonline.com/ortho/teres_major)