Teres Minor Muscle Anatomy

Teres minor is a narrow and elongated muscle (cord-like muscle) that is completely hidden by the deltoid muscle and difficult to clearly delineate it from the infraspinatus muscle because teres minor muscle fibers may be fused with fibers of the infraspinatus muscle. Teres minor is part of the rotator cuff muscles that are also known as SITS muscles. The teres minor muscle arises from an elongated oval area on the dorsal surface of the axillary border of the scapula and passes superiorly and laterally, edge to edge with the lower border of infraspinatus and behind the long head of triceps. The teres minor tendon blends with the capsule of the shoulder joint to attach to the lowest facet on the greater tubercle of the humerus. The lower part of the lateral border of teres minor muscle lies edge to edge with teres major of which the teres major then leaves it by passing forward in front of the long head of triceps.

Teres Minor Origin and Insertion

The teres minor muscle arises from an elongated oval area on the dorsal surface of the axillary border of the scapula and inserts on the lower facet of the greater tubercle of the humerus.

Teres Minor Action and Function

The Teres minor muscle helps other SITS muscles (Rotator cuff muscles) that act around the head of the humerus to stabilize the shoulder joint. Teres minor is a lateral rotator and weak adductor of the humerus and together with teres major it holds down the head of the humerus against the upward pull of the deltoid during abduction of the shoulder.

Teres Minor Blood Supply

The blood supply of Teres minor is from the posterior circumflex humeral artery which is a branch of the axillary artery. Teres minor is also supplied by the circumflex scapular artery.

Teres Minor Innervation

Teres Minor nerve supply is from the posterior branch of the axillary nerve (C5, 6) which arises from the posterior cord of the brachial plexus. Because teres minor is not clearly delineated from the infraspinatus, it is the nerve supply that helps to clearly distinguish it from the infraspinatus because teres minor is supplied by the axillary nerve while the infraspinatus is supplied by the suprascapular nerve.

Clinical importance of Teres Minor

A tear of the rotator cuff tendon leads to atrophy of Teres minor which can be detected on ultrasound scan.