Overuse of one part of the body, like a baseball pitcher’s arm, can cause tendinitis or bursitis. Tendinitis is the irritation of a tendon, the cord-like tissue that connects muscles to bones. Bursitis differs in that it is inflammation of the bursae. You can have both of these conditions at the same time, or you may only have one of them. Your healthcare provider will help determine what condition you have.