The teres major is a thick, rectangular muscle located in the upper back and shoulder region. It is often referred to as the “lat’s little helper” due to its close functional relationship with the much larger latissimus dorsi muscle. Although positioned posteriorly, its tendon wraps forward to insert on the front of the upper arm bone (humerus). The teres major helps stabilize the shoulder joint and executes powerful pulling motions of the arm.
Location and Structure of the Teres Major
The teres major originates on the posterior surface of the scapula, specifically at the inferior angle. The muscle fibers travel upward and laterally toward the axilla (armpit) region. It inserts onto the front of the humerus at the medial lip of the intertubercular groove.
This muscle is situated just beneath the teres minor, a smaller muscle that is part of the rotator cuff. The teres major forms the lower border of the quadrangular space, an anatomical landmark in the shoulder. This space serves as a passageway for the axillary nerve and the posterior humeral circumflex artery.
The nerve supply for the teres major comes from the lower subscapular nerve, which branches off the posterior cord of the brachial plexus. This innervation pathway differentiates it from the teres minor, which is supplied by the axillary nerve. Because it is not structurally connected to the capsule of the glenohumeral joint, it is not considered one of the four rotator cuff muscles.
Primary Movements Controlled by the Teres Major
The teres major moves the humerus at the shoulder joint through three distinct actions. The first is adduction, which involves pulling the arm down toward the side of the body.
The muscle also contributes to extension, which is the movement of the arm backward, such as when pulling the arm down from an overhead position. Finally, the teres major is a powerful medial rotator of the humerus, twisting the arm inward toward the chest.
These three functions—adduction, extension, and internal rotation—are performed in close synergy with the latissimus dorsi. The similar actions and shared insertion point on the humerus make the combined strength of these two muscles important for powerful pulling and climbing movements.
Understanding Teres Major Pain and Injury
Pain in the teres major often results from a muscle strain, which occurs during activities requiring sudden, forceful arm movements, like throwing a baseball or swinging a golf club. Repetitive overuse in sports such as swimming, rowing, or rock climbing can also lead to micro-trauma and inflammation. This strain typically presents as acute pain in the upper arm and the posterior axilla.
The pain from a strained teres major is commonly felt as a dull ache or sharp pain located deep in the back of the shoulder near the shoulder blade. It can also radiate to other areas, sometimes traveling down the backside of the arm toward the elbow. This pattern of pain can sometimes be mistaken for a rotator cuff injury or shoulder bursitis.
A key difference is that rotator cuff pain is often centered on shoulder abduction (lifting the arm out to the side), while teres major pain is often aggravated by forceful internal rotation and adduction. When trigger points develop within the muscle, they can limit the range of motion. This limitation makes it painful to stretch the arm across the body or reach overhead.
Initial relief strategies focus on reducing inflammation and allowing the muscle to rest. Avoiding the specific activities that caused the pain is the first step, followed by applying ice to the tender area for short periods. Once the acute pain subsides, gentle stretching, particularly those that stretch the arm across the chest, can help restore flexibility.