Shoulder pain only at scaption plane

Dear all,
I came across with a patient with right shoulder pain starting at around 80 degree shoulder elevation at scaption plane, pain increases beyond 80 degrees.
She has no pain at any other shoulder movements. Even at abduction with internal rotation, she is painless.
I observed when she is doing the elevation at scaption plane, she is kind of using the upper trapezius a lot in doing so,
also her para-scapular muscles are tight, esp lat dorsi and rhomboids.

I think this is kind of impingement problems, but why only at scaption plane?? can anyone please explain? :rolleyes:

Thanks! :)