Muscle Anatomy

Posterior Deltoid

The posterior deltoid, positioned at the rear of the shoulder, is a triangular muscle that completes the deltoid muscle group.

Arising from the spine of the scapula, the posterior deltoid's fibers spread out, attaching to the deltoid tuberosity on the humerus.

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

The primary function of the posterior deltoid is shoulder extension, drawing the arm backward. It plays a significant role in shoulder horizontal abduction, aiding in moving the arm away from the midline. The posterior deltoid contributes to overall shoulder strength and stability, particularly in activities involving pulling or reaching behind the body.