The muscles that make up the shoulder are categorized into two main groups: the rotator cuff muscles and the muscles of the shoulder girdle.
Rotator Cuff Muscles
These muscles are crucial for shoulder stability and movement. The rotator cuff muscles are:
- Supraspinatus: This muscle helps with the abduction (raising) of the arm.
- Infraspinatus: This muscle assists in external rotation of the arm.
- Teres Minor: Similar to the infraspinatus, it aids in external rotation.
- Subscapularis: This muscle is involved in the internal rotation of the arm.
These four muscles work together to keep the head of the humerus (upper arm bone) securely in the shoulder socket, facilitating a wide range of motions and providing stability [2][1].
Shoulder Girdle Muscles
Besides the rotator cuff, several other muscles contribute to the function of the shoulder girdle:
- Pectoralis Major: A large chest muscle that contributes to adduction, flexion, and internal rotation of the arm.
- Pectoralis Minor: A smaller muscle underneath the pectoralis major, that aids in the downward and forward movement of the shoulder.
- Deltoids: The large, triangular muscles that cap the shoulder, they are primarily involved in arm abduction, flexion and extension.
- Trapezius: This muscle runs from the neck, across the shoulders, and down the back, is important for scapular movement and neck support.
- Serratus Anterior: This muscle, located on the side of the chest under the arm, assists in protraction of the shoulder blade and rotation of the scapula upward.
These muscles function in synergy to enable a broad range of motion, power, and precision in the movements of the shoulder and arm.
| Muscle Group | Muscles | Function |
|---|---|---|
| Rotator Cuff | Supraspinatus, Infraspinatus, Teres Minor, Subscapularis | Stabilize the shoulder joint, facilitate rotation and abduction of the arm |
| Shoulder Girdle | Pectoralis Major, Pectoralis Minor, Deltoids, Trapezius, Serratus Anterior | Support shoulder movement, enable arm flexion, extension, adduction, and scapular movement |
Understanding the names and functions of these shoulder muscles is essential for recognizing how the shoulder joint operates, and identifying potential issues in this area.
