shoulder or lumbar region, including bones and joints The bone is the scapula. clavicle and humerus joints are joints glenohumeral, acromioclavicular and sternoclavicular The shoulder joint has the greatest range of motion of any other joint in the body, but is more prone to injury. The large deltoid muscles provide most of the power for shoulder movement. Beneath the deltoid muscle are four rotator muscles that support movement. Tendons attach these muscles to bones. swivel joint It consists of the muscles and tendons that hold the upper arm in the shoulder joint.