uptill 15 degrees vertical rotator cuff is responsible for 15 degrees but 15-90 degrees , deltoid is responsible.so now u can find out that uptill how many degrees ur arm moves upward painful.well i recommend u to go to a good physiotherapist and ask him to apply tens and do mobilisation of the glenohumeral joint,it would be helpful
why would tens and joint mobilisations be helpful if it was a rotator cuff tear/strain?