Symptoms include pain on the outside of your elbow, often extending down the forearm. The pain, which may occur constantly or only when lifting, can worsen when gripping items, turning your hand, or swinging your arm. Your elbow may also swell. The cause is typically overuse of the elbow joint when swinging a racket in sports activities. Any activity that involves extending your wrist or rotating your forearm, such as hammering, raking, or painting, can also cause tennis elbow.