Corpus: Supraspinatus muscle

The supraspinatus muscle belongs to the dorsal group of shoulder muscles. It is part of the so-called rotator cuff.

The ventral muscle fibers originate from the supraspinatus fossa on the back of the scapula and largely fill it. The dorsal fibers originate from the spine of the scapula and the supraspinatus fascia. The insertion of the supraspinatus muscle is at the greater tubercle of the humerus, where it contributes to forming the rotator cuff and stabilizes the shoulder joint.

The innervation of the supraspinatus muscle is provided by the suprascapular nerve from the brachial plexus (segments: C4-C6).

The supraspinatus muscle, together with the deltoid muscle, is responsible for the abduction and external rotation of the upper arm. With the arm at the side or at a small abduction angle — under about 15° — it is the most important agonist for moving the arm away from the body. Afterward, the deltoid muscle does the main work. An additional function of the supraspinatus muscle is the tensioning of the relatively loose capsule of the shoulder joint. In coordination with the other muscles of the rotator cuff, the head of the humerus (Caput humeri) is moved medially at the start of the shoulder movement and thus centered on the glenoid cavity.

Degenerative changes of the supraspinatus muscle or its tendon (tendinopathy) arise due to a narrowing of the subacromial space and intrinsic factors as part of the aging process and chronic overuse. Clinically, an impingement syndrome is evident. Furthermore, forceful arm movements (e.g., in sports) can lead to a rupture of the muscle or its tendon (supraspinatus tendon rupture). The muscle is the most frequently injured muscle of the rotator cuff.