The shoulder is a ball-and-socket joint with three main bones: the upper arm bone (humerus), collarbone (clavicle), and shoulder blade (scapula). These bones are held together by muscles, tendons, and ligaments. The shoulder joint has the greatest range of motion of any joint in the body and because of its mobility, it tends to be more susceptible to injury.
Shoulder pain can originate in the joint or in any of the surrounding muscles, ligaments or tendons and usually worsens with activities or movement of your arm or shoulder. Injuries are the most common cause of shoulder pain and should be treated by a doctor. They usually occur during sports activities, work-related tasks or projects around the home.