Tennis elbow, otherwise known as lateral epicondylitis, is a common injury that causes pain at the outer portion of the elbow and forearm due to inflammation around the elbow joint. The outside portion of the elbow can often be painful, tender, or swollen. Symptoms usually affect everyday tasks such as holding a cup, turning a doorknob, or simply shaking hands. The pain is generally due to repetitive use of the muscles in that part of the arm, most commonly from an occupational repetitive motion. Surprisingly, only 5% of people that have tennis elbow actually play tennis.