This is a common condition in people who use the extensor muscles of their forearms vigorously, and not only in tennis players. It is caused by minute tears in the origin of the forearm extensor muscles. The patient complains of pain just distal to the lateral epicondyle of his humerus, without any history of trauma. The pain is worse when you press over his radio-humeral joint during pronation and supination. It lasts for months, or years, and may eventually disappear spontaneously. You can hasten its departure like this.
EPICONDYLITIS. Inject hydrocortisone suspension 2.5 ml with an equal volume of 2% lignocaine into the tender area. One injection has an 80% chance of success, and a second one 2 or 3 weeks later another 10%. Take very careful aseptic precautions, and don't give him more than three injections. If his disability is severe, refer him for a muscle slide on the extensor origin.