Hello there, If this is a dull type of pain it is a cause of strain in the extensor muscles of hand and fore arm. If this is a sharp pain and at the joint only then it is a cause of extensor tendinopathy.. Since this pain lasts a year back conservative management like following would be helpful - Cryopack over the painful point followed by deep transverse friction massage followed by hydro collateral pack followed by myofascial release technique followed by high voltage galvanic stimulation/ surged faradism under tension followed by free exercises and inter ferential therapy if required followed by pulsed ultrasound therapy followed by kinesio taping technique weekly 2-3 sessions of physiotherapy for about 4 weeks including rehabilitation protocol.. must take physiotherapy from a cerified / registered physiotherapist if possible from a physio having specialisation in musculoskeletal conditions..... wish you a pain free hand soon.....