The muscles directly contributing to the movements and stability of the shoulder joint (glenohumeral joint) include the four rotator cuff muscles, the deltoid, the teres major, the pectoralis major and the latissimus dorsi.
Here's a breakdown:
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Rotator Cuff Muscles (4): These muscles are crucial for shoulder stability and rotation.
- Supraspinatus: Abducts the arm.
- Infraspinatus: Externally rotates the arm.
- Teres Minor: Externally rotates and adducts the arm.
- Subscapularis: Internally rotates the arm.
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Deltoid: A large, multi-headed muscle that abducts, flexes, and extends the arm.
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Teres Major: Assists in internal rotation, adduction, and extension of the arm. While not part of the rotator cuff, it works closely with the latissimus dorsi.
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Pectoralis Major: Adducts, flexes, and internally rotates the arm.
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Latissimus Dorsi: While primarily a back muscle, it significantly impacts shoulder function by adducting, extending, and internally rotating the arm.
While muscles like the trapezius, serratus anterior, pectoralis minor, and rhomboids influence the shoulder girdle (scapula), the eight muscles listed above most directly affect the glenohumeral joint itself.
