Overview
Teres minor is a simple muscle in a complicated area of structural anatomy. It’s a flat muscle that lies up under the inferior belly of the infraspinatus and posterior deltoid. It is the border of the rotator cuff muscle. Consequently, teres minor covers the long head of the triceps, which attaches to the infraglenoid tubercle and separates it from teres major.
Origin
- lateral border of the scapula
Insertion
- greater tubercle of the humerus and posterior surface of the joint capsule
Function
- lateral rotation of the humerus
Innervation
- axillary nerve C5-C6
Functional Considerations
It is easy to think of it as the 4th head of infraspinatus. It originates from the lateral border of the scapula It is covered by the inferior head of the infraspinatus. Also, it attaches to the complex fascial structure that covers the infraspinatus muscle.
Teres Minor inserts on the posterior greater tubercle of the humerus. The inferior belly of infraspinatus inserts with teres minor to the fascia of the posterior joint capsule. This tendon attachment of the inferior infraspinatus is notably inferior and medial to the insertion of the other infraspinatus bellies.
It appears to act synergistically with the infraspinatus, even though it has a different nerve supply. Primarily, it secures the humeral head while externally rotating the humerus. Other actions, like the abduction of the humerus and extension of the shoulder, seem possible based on its location. However, electromyographical studies don’t support those possibilities.
Anomalies, Etc.
A number of sites report that the attachment with infraspinatus as a variable. Others state that attachment with infraspinatus is the norm. None of the reports that I reviewed offered references to specific studies that quote percentages.
Wikipedia entry for teres minor.
Posts Related to Teres Minor
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Tony Preston has a practice in Atlanta, Georgia, where he sees clients. He has written materials and instructed classes since the mid-90s. This includes anatomy, trigger points, cranial, and neuromuscular.
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