Deltoid Muscle Movements: Understanding Shoulder Joint Actions

The deltoid muscle has three main divisions, each with its own specific movement:

- The anterior deltoid (front of the shoulder) flexes (brings forward) the arm at the shoulder joint.

- The middle deltoid (side of the shoulder) abducts (moves away from the body) the arm at the shoulder joint.

- The posterior deltoid (back of the shoulder) extends (straightens) the arm at the shoulder joint.

In addition to these three main movements, the deltoid muscle also assists with:

- Horizontal abduction (moving the arm away from the body in a horizontal plane)

- Horizontal adduction (moving the arm toward the body in a horizontal plane)

- Internal rotation (turning the palm of the hand inward)

- External rotation (turning the palm of the hand outward)

The deltoid muscle is innervated by the axillary nerve.