One difference between radial tunnel syndrome and tennis elbow is the exact location of the pain. In tennis elbow, the pain starts where the tendon attaches to the lateral epicondyle. In radial tunnel syndrome, the pain is centered about two inches further down the arm, over the spot where the radial nerve goes under the supinator muscle. Radial tunnel syndrome may also cause a more achy type of pain or fatigue in the muscles of the forearm.