Tennis Elbow? Pseudo tennis elbow

True tennis elbow is a tendinitis of the extensor muscles and that tendon group originates on the humerus above the elbow. When there is pain that is below the elbow, and is in the lateral forearm, it might actually be an annular ligament sprain with a minimally subluxed radial head. The neck, just below the radial head (radius bone) is 2 to 3 fingers below the lateral elbow joint. It can be exquisetely tender when isolated. there will be a reduction of proximal supination, though oftentimes missed as the distal supination increases and compensates. However, careful over pressure comparing both forearms will be indicative. Traction to the radius will be lacking on the painful side as the mechanism of injury may be repetive trauma or a heavy lift that tractions the radius bone inferiorly. You will note less space between the end of the radius and the wrist.  The radial head is round with a flat edge where the annulkar (ring) ligament wraps around it. So a traction injury is a bit like pulling a funnel down, because part of the ligament is significantly stretched, being pulled beyond the neck into the radial head..
Treatment? Gently grasp the radius, stabilize the upper arm, oscillate with moderate force after taking up the slack, 30 reps. Very effective and long lasting. Of course other rehab things can be pursued, this part addressed the primary restriction and positional ligament strain. If you unyielding tennis elbow, do have the above joint evaluated. Best Wishes, Jerry