At uppermost section of the arm and top section of shoulder is the deltoid muscle, the largest shoulder muscle. Other muscles that aid shoulder and arm movement include the 4 rotator cuff muscles (Infraspinatus, Subscapularis, Supraspinatus and the Teres major muscles), Tricep brachii, Pectoralis major, Pectoralis minor, Bicep brachii and Latissimus dorsi.