Teres Minor Muscle Anatomy

Location & Overview

The teres minor is a narrow muscle located in the area of the upper back and shoulder. The distal part of the teres minor is covered by the deltoid. Sometimes muscle fibres from the infraspinatus can be fused with fibres of the teres minor. The teres minor is located inferiorly to the infraspinatus muscle and superior to the teres major muscle ^{[1] [2]}.

The teres minor muscle is one of the four rotator cuff muscles of the shoulder. The remaining three are: the supraspinatus, infraspinatus and subscapularis. A useful acronym to remember the rotator cuff muscles is ‘SITS’. Collectively the rotator cuff muscles are able to provide stabilisation to the glenohumeral joint; which is the ball and socket joint where the head of the humerus sits within the glenoid cavity ^{[3] [4]}.

Origin & Insertion

The teres minor originates on the posterior surface of the scapula, specifically on the lateral border. The insertion is then located on the inferior facet of the greater tubercle of the humerus. The upper fibres of the tendon blend into the capsule of the shoulder joint, whereas the lower fibers insert directly onto the humerus ^{[5] [6]}.

Actions

The primary action of the teres minor is lateral rotation (or external rotation) of arm. It also works alongside the other rotator cuff muscles to achieve stabilisation of the humerus in the glenohumeral joint. Additionally, it can provide very weak assistance during adduction of the shoulder ^{[7] [8] [9]}.

Innervation

Axillary nerve (C5, C6) innervates the teres minor. This nerve originates from the brachial plexus and passes through the quadrangular space into the posterior scapula region ^[10].

Blood Supply

Blood is supplied to the teres minor from the subscapular artery and one of its branches, the circumflex scapular artery. It also received blood from the posterior circumflex artery ^{[11] [12]}.