Teres Major Muscle: Location and Actions

The teres major muscle is a small, round muscle lying along the lateral border of the scapula. It forms the inferior border of both the triangular space and quadrangular space. The muscle gets its name from its shape and size. Teres means “round” in Latin, and the term major refers to it being the larger of two muscles, the teres minor muscle lying just superior to the major. Both the teres major and minor are similar in shape, only the major is larger. It can be palpated in the trough between the lateral scapula and the latissimus dorsi, but is deeper than the latissimus.

See Teres Major Trigger Points

The teres major share the same functions as the latissimus dorsi in internally rotating, adducting, and extending the shoulder, especially from the flexed position. 1McFarland, Edward G., and Tae Kyun. Kim. Examination of the Shoulder: The Complete Guide. New York: Thieme, 2006. The teres major acts more strongly when the rhomboids and levator scapulae fix the inferior angle of the scapula 2Simons, David G., Janet G. Travell, Lois S. Simons, and Janet G. Travell. “Chp. 25: Teres Major Muscle.” Travell & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Baltimore: Williams & Wilkins, 1999. 587-595.,3Floyd, R. T., and Clem W. Thompson. Manual of Structural Kinesiology. Dubuque, IA: WCB/McGraw-Hill, 1998. 47. or otherwise the scapula would move forward toward the arm. It is sometimes called the lat’s little helper.

Kinesiology: The Skeletal System and Muscle Function

Both the teres major and the latissimus dorsi wrap around from the back of the armpit, with the latissimus twisting around the teres major to help form the axilliary fold, both attaching to the front of the upper humerus. The borders of the two muscles are joined for a short distance near the humeral attachments. They do not share the same attachments below, however. The teres major attaches to the scapula and the latissimus attaches to the wall of the chest.  4Simons, David G., Janet G. Travell, Lois S. Simons, and Janet G. Travell. “Chp. 25: Teres Major Muscle.” Travell & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Baltimore: Williams & Wilkins, 1999. 587-595. Together, the two form the thick posterior wall of the armpit.

teres major muscle illustration
Teres Major Muscle

Teres Major Origin, Insertion, and Action

Origin: Dorsal (posterior) surface of the lateral border of the scapula, just above the inferior angle below the teres minor.

Insertion: Medial lip of the intertubercular groove of the humerus just below the insertion of the subscapularis.

Action: Internal rotation, adduction, and extension of the glenohumeral joint. More active during resisted adduction and extension of the arm from the flexed position to the posteriorly extended position. Weak adduction of the arm when acting alone but strongly adducts arm when the scapula is fixed by the rhomboid and levator scapulae. Also active during the backward swing of the arm when walking. Assists the latissimus dorsi in the wood chopping movement. Activated when writing or typing on a keyboard. 5Simons, David G., Janet G. Travell, Lois S. Simons, and Janet G. Travell. “Chp. 25: Teres Major Muscle.” Travell & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Baltimore: Williams & Wilkins, 1999. 587-595.,6Floyd, R. T., and Clem W. Thompson. Manual of Structural Kinesiology. Dubuque, IA: WCB/McGraw-Hill, 1998. 47.

See Teres Major Trigger Points and Referred Pain

Sources   [ + ]

1. McFarland, Edward G., and Tae Kyun. Kim. Examination of the Shoulder: The Complete Guide. New York: Thieme, 2006.
2, 4, 5. Simons, David G., Janet G. Travell, Lois S. Simons, and Janet G. Travell. “Chp. 25: Teres Major Muscle.” Travell & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Baltimore: Williams & Wilkins, 1999. 587-595.
3, 6. Floyd, R. T., and Clem W. Thompson. Manual of Structural Kinesiology. Dubuque, IA: WCB/McGraw-Hill, 1998. 47.