Muscle Anatomy

Middle Deltoid

The middle deltoid, positioned centrally on the shoulder, forms a substantial part of the deltoid muscle group, creating the rounded contour of the shoulder.

Emerging from the acromion process of the scapula, the middle deltoid's fibers extend laterally to attach to the deltoid tuberosity on the humerus.

The muscle inserts onto the deltoid tuberosity, a prominence on the lateral surface of the humerus.

The primary function of the middle deltoid is shoulder abduction, lifting the arm laterally away from the body. It contributes significantly to overall shoulder strength and stability, playing a crucial role in various arm movements, including those involving lifting, pushing, or reaching outward.