Shoulder and arm movement. Artwork of the muscles of the arm and shoulder from the front, with red arrows showing the direction of movement when shrugging the shoulders (scapular elevation). A small amount of arm abduction (moving the arm upwards in the plane of the body) has also occurred. The shoulder is a ball-and-socket joint that has a wide range of possible movements. The large muscle forming the rounded corner of the shoulder is the deltoid muscle. This diagram shows the right arm and shoulder. For the left arm and shoulder, see C016/6788.