The deltoid tuberosity of the humerus lies proximally about a third of the way to the elbow and provides an attachment point for the deltoid muscle. The deltoid is a triangular muscle with three attachment points: the humerus, the clavicle, and the scapula. Due to its many bands of muscle fibers, the deltoid is able to produce several distinct arm movements, including medial rotation, flexion, abduction, extension, and lateral rotation.
