Tennis elbow is a common term for a condition caused by overuse of arm, forearm, and hand muscles that results in elbow pain. You don't have to play tennis to get this, but the term came into use because it can be a significant problem for some tennis players.
Tennis elbow is caused by either abrupt or subtle injury of the muscle and tendon area around the outside of the elbow. Tennis elbow specifically involves the area where the muscles and tendons of the forearm attach to the outside bony area (called the lateral epicondyle) of the elbow. Your healthcare provider may call this condition lateral epicondylitis.