The elbow is where the bone in your upper arm meets the two bones in your lower arm. There is a bump on the outside of your elbow at the bottom of your upper arm bone. It is the lateral epicondyle. A few tendons attach here. Tendons attach muscles to bone. These muscles are used to pull your wrist and fingers up. When these tendons get sore and swollen from overuse, you have lateral epicondylitis. It is also called tennis elbow. This is a common problem in tennis players. It may also happen with other activities or sports. You are more likely to have this problem in the arm you use most. It can happen in either arm. Most people get better with treatment and do not need surgery.