teres minor and major

3 min read 14-03-2025

The teres minor and major muscles, located in the posterior (back) shoulder, play crucial roles in shoulder movement and stability. Often overlooked, understanding their anatomy, function, and potential for injury is vital for athletes, physical therapists, and anyone interested in maintaining shoulder health. This article will delve into these important muscles, providing a comprehensive overview.

Teres Minor Muscle: Anatomy and Function

The teres minor is a smaller, more superficial muscle compared to its counterpart.

Anatomy of the Teres Minor

Origin: Lateral border of the scapula (shoulder blade).
Insertion: Greater tubercle of the humerus (upper arm bone).
Innervation: Axillary nerve (C5-C6).

Function of the Teres Minor

The teres minor's primary function is external rotation of the humerus. This means it helps rotate your arm outward away from your body. It also plays a secondary role in shoulder abduction (raising the arm away from the side) and horizontal abduction (moving the arm away from the midline of the body). Importantly, it contributes to overall shoulder joint stability.

Teres Major Muscle: Anatomy and Function

The teres major is a larger, deeper muscle positioned inferior to the teres minor.

Anatomy of the Teres Major

Origin: Inferior angle of the scapula.
Insertion: Medial lip of the intertubercular groove of the humerus.
Innervation: Lower subscapular nerve (C5-C6).

Function of the Teres Major

The teres major is a powerful internal rotator of the humerus. This means it rotates the arm inward toward the body. It also contributes to shoulder extension (moving the arm backward) and adduction (moving the arm towards the body). Like the teres minor, it provides important shoulder stability.

Synergistic Actions and Importance of the Teres Muscles

The teres minor and major, although having opposing primary actions (external vs. internal rotation), work synergistically with other rotator cuff muscles (supraspinatus, infraspinatus, subscapularis) to provide coordinated shoulder movement. Their combined function is critical for:

Smooth, controlled shoulder motion: Precise movements like throwing, swimming, or lifting require coordinated action of these muscles.
Shoulder joint stability: Maintaining the integrity of the shoulder joint and preventing dislocation.
Preventing injury: Weakness or imbalance in these muscles can significantly increase the risk of rotator cuff tears and other shoulder injuries.

Common Injuries Affecting the Teres Muscles

While less frequently injured than some other rotator cuff muscles, the teres minor and major can be affected by:

Strains: Overuse or sudden forceful movements can cause muscle strains, leading to pain and decreased function.
Tears: Although less common than tears in other rotator cuff muscles, tears can occur, particularly with repetitive overhead activities or trauma.
Impingement: Inflammation and irritation of the muscles due to compression within the shoulder joint.

How to identify Teres Muscle Injuries:

Identifying issues with the teres muscles often requires a professional diagnosis. Symptoms can include:

Pain in the back of the shoulder
Weakness when rotating the arm
Decreased range of motion
Clicking or popping in the shoulder

Strengthening and Rehabilitation

Strengthening exercises specifically targeting the teres minor and major can help prevent and rehabilitate injuries. These exercises often involve external and internal rotations of the arm, sometimes with resistance.

Examples include:

External rotation exercises: Lying on your side with a weight in your hand, rotating your arm outward.
Internal rotation exercises: Similar position, but rotating your arm inward.

Consult a physical therapist or athletic trainer for a customized program.

Conclusion: The Importance of Teres Muscle Health

The teres minor and major muscles are essential components of the shoulder complex. Their combined actions ensure smooth, controlled movement and stability. Understanding their anatomy, function, and potential for injury is crucial for maintaining shoulder health and preventing debilitating problems. Regular exercise, proper warm-up, and addressing any pain or weakness promptly are key to maintaining the health of these important muscles. Remember to consult a healthcare professional for diagnosis and treatment of any shoulder pain or injury.