The teres major muscle is a muscle in the upper back and shoulder region. It is a thin, elongated muscle that originates from the lower border of the scapula (shoulder blade) and inserts into the humerus (upper arm bone).
The teres major muscle is part of a group of muscles called the rotator cuff muscles, which are responsible for rotating and stabilizing the shoulder joint. It works in conjunction with other muscles, including the infraspinatus and supraspinatus, to help rotate the arm outward (external rotation) and to assist in pulling the arm down and back (adduction).
The teres major muscle is important for a variety of upper body movements, including throwing a ball, lifting weights, and pulling oneself up. It is also involved in activities such as swimming and rowing.
Injury to the teres major muscle can occur from overuse or from sudden, high-force movements, such as those that occur during contact sports. Treatment may involve rest, ice, physical therapy, and in some cases, surgery.