Shoulder muscles move the shoulders, shoulder blades and upper arms.
The main shoulder muscles are trapezius, deltoid, pectoralis major and 4 rotator cuff muscles: subscapularis, supraspinatus, infraspinatus and teres minor. The list of muscles and their functions are presented below. Muscle attachments (origins, insertions) are described in the video at the bottom of this article and in the articles about the shoulder girdle and shoulder blade.
Muscles at the Back of the Shoulder
Picture 1. Muscles at the back of the shoulder
(free image use)
- Trapezius elevates and depresses the shoulder and brings together (retracts) the shoulder blades.
- Deltoid (posterior and middle head) moves the upper arm sideways (abduction), brings it to the body (adduction), extends it backwards and rotates it outwards (external rotation).
- Rotator cuff muscles:
- Levator scapulae elevates the shoulder.
- Teres major extends the upper arm backwards and rotates it inwards (internal rotation).
- Rhomboid major and minor bring together (retract) the shoulder blades.
- Serratus anterior moves the shoulder blades apart (protraction).
- Triceps brachii extends the upper arm backwards and moves it toward the body (adduction).
Muscles at the Front of the Shoulder
- Deltoid (anterior head) flexes the upper arm forwards and rotates it inwards (internal rotation).
- Pectoralis minor draws the shoulder blade forwards and downward.
- Coracobrachialis flexes the upper arm forwards.
- Biceps brachii flexes and supinates the forearm and slightly flexes the upper arm in the shoulder.
Video 1. 3D presentation of the shoulder muscles
with their attachments and functions