Teres Major Location
Teres major is a shoulder muscle that extends from the bottom part of the posterior surface of the shoulder blade (scapula) to the upper front part of the arm bone (humerus). Unlike teres minor, teres major is not a part of rotator cuff.
Teres major originates from the posterior surface of the inferior angle and bottom part of the lateral angle of scapula .
Teres major inserts to the medial lip of the intertubercular (bicipital) groove on the anterior side of the humerus .
- Adducts (brings to the body) the arm in the shoulder joint
- Medially (internally) rotates the arm
- Extends the arm backwards
- Reference: 
Teres major is innervated by a lower subscapular nerve (nerve roots C5-C7) .
Teres major gets blood via the subscapular and circumflex scapular arteries .
Picture 1. Teres major anatomy: origin, insertion, action
(free image use)
Video 1. Teres major anatomy: origin, insertion, actions, relations to other muscles
Related anatomy: shoulder muscles
Teres Major Tear
Teres major tear is common in sports with frequent shoulder movements: pitching in baseball, rowing, swimming, rock climbing, tennis, golf and water skiing .
The main symptom of a teres major tear is a sudden sharp pain in the shoulder, upper arm and armpit . The area near the bottom of the shoulder blade can become swollen.
Teres Major Strength Test
You lie on the table face down and place your hand on the lower back with the back of the hand touching the skin. An examiner places one hand on the elbow and with the other hand stabilizes the shoulder on the affected side.
The examiner applies moderate resistance against the superior surface of the elbow and asks you to push the elbow toward the ceiling. Decreased strength–compared to the other side–speaks for a teres major injury [Video 2, ref. 4].
Video 2. Teres major test
A doctor can confirm a diagnosis of the teres major rupture by a magnetic resonance imaging (MRI) .
Treatment of teres major rupture can include only physiotherapy, which may not result in full recovery, or by an arthroscopic procedure or open surgery.