The deltoid muscles are shoulder muscles of the human body. These muscles are broken into three groups, which are the anterior, lateral, and posterior muscles. The anterior deltoid is the muscle located on the front area of the shoulder. This muscle is primarily used by the body to lift the arms straight overhead.
Located superior to the shoulder joint, the deltoid muscle works with the supraspinatus to abduct the arm at the shoulder. On the anterior side of the shoulder, the coracobrachialis, serratus anterior, pectoralis major, and pectoralis minor muscles work as a group to flex and adduct the scapula and humerus anteriorly toward the sternum.
It is named after the Greek letter delta, which is shaped like an equilateral triangle. The deltoid is attached by tendons to the skeleton at the clavicle (collarbone), scapula (shoulder blade), and humerus (upper arm bone).