The shoulder is a very complex piece of machinery. As long as all the parts are in good working order, the shoulder can move freely and painlessly. Many people refer to any pain in the shoulder as bursitis. The term bursitis really only means that the part of the shoulder called the bursa is inflamed. Tendonitis is when a tendon gets inflamed and can be another source of pain in the shoulder.
Many different problems can cause inflammation of the bursa or tendons.
Impingement syndrome is one of those problems. The rotator cuff connects the humerus to the scapula. Tendons attach muscles to bones. Muscles move the bones by pulling on the tendons. The rotator cuff helps raise and rotate the arm.