The teres major muscle medially rotates, adducts, and extends the shoulder joint.  Shortness of this muscle limits shoulder flexion and can impede depression and lateral rotation of the humeral head.  

Actions

• Extends the shoulder (glenohumeral joint)
• Adducts the shoulder (g/h joint)
• Medially rotates the shoulder (g/h joint)

Origin

• Lateral side of the inferior angle and lower half of the lateral border of the scapula

Insertion

• Crest of the lesser tubercle of the humerus

Nerve Innervation

• Lower Scapular