The shoulder joint is a region of the upper limb that is made up of multiple muscles, including the subscapularis, supraspinatus, infraspinatus, teres major and minor, serratus major, pectoralis, subclavius, and more.
The teres major muscle plays a vital role in shoulder movement, although it is not part of the rotator cuff. In this article, we will explore the origin, insertion, innervation, and function of this important muscle, and its relationship with the latissimus dorsi muscle.
Introduction
Teres major means “big round muscle.”(1) This small muscle is located directly below teres minor on the border of the shoulder blade. This muscle synergistically works with the latissimus dorsi muscle for the different motions of the arm forming the posterior axillary fold.(2)(3)
| Anatomy | Origin | Insertion | Action |
|---|---|---|---|
| Teres Major Muscle | Inferior angle of scapula | Medial lip of intertubercular groove of humerus | Adduction, medial rotation and extension of humerus |
Anatomy
Origin
Teres major muscle origins from two locations which includes the lower third of the lateral border of the scapula (below the teres minor) and an oval area on the inferior angle of the scapula.(3)(4)
Insertion
The muscle passes posterior to the coracobrachialis muscle and anterior to the long head of the triceps brachii muscle before attaching to the medial lip of the intertubercular sulcus of the humerus.(3)
Action
Together with the latissimus dorsi it medially rotates, adducts, and extends the arm at the shoulder joint. It also upwardly rotates the scapula at the glenohumeral and scapulocostal joints. The teres major, however, could only move the arm weakly to the side when acting alone.(3)(5)
Therefore, these muscles are utilized in a variety of sports, including weightlifting, skiing, hiking, gymnastics, swimming, tennis, basketball, pitching, and throwing.(2)
Innervation
The nerve supply for the teres major muscle is from the lower subscapular nerve, C5, 6, 7, from the posterior cord of the brachial plexus.(3)
Relationship with the Latissimus Dorsi Muscle
The teres major muscle has a close relationship with the latissimus dorsi muscle. It runs parallel to the fibers of the latissimus dorsi and inserts together with it at the crest of the lesser tubercle of the humerus.
During their course, both muscles form the posterior axillary fold. Sometimes, their muscle bellies or insertion tendons even blend together, and their motions in the shoulder joint are basically identical.
Trigger Points
Trigger Points of teres major may be palpated by having the patient lie supine with the arm abducted nearly 90 degree and laterally rotated.(3)
First reaching under the arm and feeling for the sharp outside edge of the shoulder blade is important. Then using the thumb and fingers grasping the mass of muscle lying right next to it locates the latissimus dorsi and teres major muscles.
The trigger points are located 2 to 3 inches above the sharp lower angle of the shoulder blade at the posterior axillary fold, deeper and more medial than latissimus dorsi.
Trigger points rarely form in the teres major without first appearing in the latissimus dorsi, but the radiation of their pain are significantly different.(2,6)
Satellite trigger points: Long head of the triceps brachii, latissimus dorsi, posterior deltoid, teres minor, and subscapularis.(6)
Pain Pattern
Pain from the trigger points is deep and sharp which radiates into posterior glenohumeral joint and an oval zone (5-10cm) of pain in posterior deltoid area (can radiate strongly to long head of biceps brachii).
Additionally, diffuse pain can also involve the dorsum of forearm and rarely, if ever, to the scapula or elbow.(3,7)
Abducting the arm and placing it against the homolateral ear is challenging for the patient. Reaching up and forward causes pain with a little mobility restriction.(6)
Perpetuating Factors
Different kinds of movements and actions can illicit pain in teres major trigger points which includes overuse with the arms upward and out; rowing, swimming crawl stroke, lifting weights overhead, or using exercise machines that repeat these movements, using a crutch, compensating with the arms for painful low back muscles, and driving a vehicle that requires heavy steering effort.(8)
Exercises
Classic rotator cuff exercises include external rotation variations, standing arm raises with weight, and lying-on-your-stomach arm lifts.
Research has identified some exercises as more effective than others:
- Side-lying external rotation: A 2004 study by Reinold et al. found the highest activation of infraspinatus and teres minor during this exercise. This is expected, as these muscles are responsible for external rotation.
- Banded external rotation: In a study comparing three exercises (prone Y, prone external rotation, and standing banded external rotation), the banded external rotation demonstrated the least posterior deltoid activation while maintaining similar infraspinatus activation.
- Full can exercise: In a study comparing empty can, full can, prone Y, prone external rotation, and banded external rotation, all exercises activated the supraspinatus to equally high levels. However, the full can exercise demonstrated the least posterior and middle deltoid activity.
Addressing Deltoid Activation
Physical therapists often encounter questions about whether deltoid activation during rotator cuff exercises matters. The answer depends on individual circumstances.
In cases where a person has strong deltoids or is sensitive to higher loads, exercises like side-lying external rotation or full can may be better options, as they preferentially target the rotator cuff over the deltoids. However, in other cases, deltoid activation might not be a significant concern.
General Recommendations
For most people, performing 2-4 sets of 10-20 reps close to fatigue, 2-3 times a week is a general recommendation for these exercises. However, for specific guidance, always consult a reliable healthcare practitioner for individual needs.
Beyond Classic Rotator Cuff Exercises
Strength training movements like lateral raises and overhead pressing not only activate the rotator cuff but also move the shoulder through a greater range of motion and build strength around the scapula, arms, and trunk. These exercises have been shown to increase activation of the supraspinatus, infraspinatus, serratus anterior, lower trap, and deltoid muscles.
If you experience front shoulder discomfort during these movements, consider transitioning to more pulling exercises, which can be more tolerable for the shoulder. Keep in mind that a combination of exercises, including compound movements like pressing and pulling or lateral raises, can help build a more robust system and increase shoulder tissue capacity.
Conclusion
The teres major muscle, although not part of the rotator cuff, plays a crucial role in shoulder movement. Its close relationship with the latissimus dorsi muscle enables it to work in tandem for effective and smooth motion in the shoulder joint.
Understanding the anatomy and function of the teres major muscle can provide insight into its significance in maintaining shoulder stability and strength.
References
1. Claire Davies AD. The Trigger Point Therapy Workbook- Your Self-Treatment Guide for Pain Relief. 2013.
2. Finando D, Ac L. Trigger Point Self-Care Manual- For Pain-Free Movement. Inner Traditions / Bear & Company; 2005.
3. DAVID G. SIMONS, JANET G. TRAVELL LSS. Travell & Simons’ myofascial pain and dysfunction – the trigger point manual Volume 1. 2nd editio. 1999.
4. Richler P, Hebgrn E. Trigger Points and Muscle Chains in Osteopathy. 2009.
5. Muscolino JE. The Muscle and Bone Palpation Manual with Trigger Points, Referral Patterns and Stretching. 2009.
6. Finando D, Finando S. Trigger Point Therapy for Myofascial Pain. 2005.
7. Niel-asher S. The Concise Book of Trigger Points. 2nd editio. 2008.
8. Starlanyl DJ, Sharkey J. Healing through trigger point therapy – a guide to fibromyalgia, myofascial pain and dysfunction. Vol. 15. 2016.
MD, PhD. Physical Medicine & Rehabilitation Physician from São Paulo - Brazil. Pain Fellowship in University of São Paulo.