teres major and minor

3 min read 14-03-2025

The teres major and minor muscles, often overlooked, play crucial roles in shoulder stability and movement. Located in the posterior (back) of the shoulder, these muscles contribute significantly to arm rotation, extension, and adduction. Understanding their anatomy, function, and potential injuries is essential for athletes, fitness enthusiasts, and healthcare professionals alike.

Anatomy of the Teres Major and Minor Muscles

Both muscles originate on the scapula (shoulder blade) and insert on the humerus (upper arm bone), but their specific attachments and functions differ slightly.

Teres Major Muscle

Origin: Inferior angle of the scapula (lower corner of the shoulder blade).
Insertion: Medial lip of the intertubercular sulcus of the humerus (a groove on the upper arm bone).
Innervation: Lower subscapular nerve (C5-C6).

Teres Minor Muscle

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

Notice the difference in insertion points: Teres major inserts medially, while Teres minor inserts laterally on the humerus. This anatomical distinction contributes to their different roles in shoulder movement. Both are part of the rotator cuff muscle group, although Teres Major is sometimes excluded from this classification.

Function of the Teres Major and Minor Muscles

The teres major and minor muscles work synergistically and with other muscles to perform various shoulder actions. Their combined efforts are crucial for maintaining shoulder health and function.

Teres Major Muscle Function

Shoulder Extension: Pulling the arm backward.
Medial Rotation: Rotating the arm inward.
Adduction: Moving the arm towards the body.

Because of its insertion point and nerve supply, the Teres Major is often grouped with the latissimus dorsi, sharing similar actions in arm movement.

Teres Minor Muscle Function

External Rotation: Rotating the arm outward.
Shoulder Extension: Assists in pulling the arm backward.
Shoulder Horizontal Abduction: Moving the arm away from the body in a horizontal plane.

The teres minor’s primary function is external rotation of the shoulder, a crucial movement for many activities, from throwing a ball to swimming.

Common Injuries Affecting the Teres Major and Minor Muscles

While less frequently injured than some other shoulder muscles, the teres major and minor can still be affected by various conditions.

Teres Major Injuries

Muscle Strain: Overuse or sudden forceful movements can lead to strains, ranging in severity from mild to severe tears.
Tendinitis: Inflammation of the tendon connecting the muscle to the bone.
Labral Tears: While not directly a teres major injury, dysfunction can contribute to instability leading to labral tears.

Teres Minor Injuries

Muscle Strain: Similar to the teres major, overuse or trauma can cause strains.
Rotator Cuff Tear: This is a more severe injury often involving multiple muscles in the rotator cuff, including the teres minor.

Proper warm-up, appropriate training techniques, and focusing on balanced strength and flexibility are crucial in preventing injuries to these important shoulder muscles.

Strengthening the Teres Major and Minor Muscles

Incorporating exercises that target these muscles is key to maintaining shoulder health and preventing injuries. Here are some examples:

External Rotation Exercises: These are crucial for the teres minor, using resistance bands or weights.
Rows: Various rowing variations effectively work the teres major and other back muscles.
Pull-ups: This compound exercise powerfully engages the teres major.

Remember to consult a healthcare professional or certified trainer for personalized exercise programs based on your fitness level and any existing conditions.

Conclusion

The teres major and minor muscles are integral components of the shoulder complex. Understanding their anatomy, function, and potential injuries is vital for preventing issues and ensuring optimal shoulder health and performance. By incorporating targeted exercises and maintaining proper training techniques, you can strengthen these muscles and reduce the risk of injury. Remember to always consult a professional for personalized advice and treatment.