How To Treat Severe Pain In Left Shoulder Despite Taking Prednisone For PMR?

I have PMR and have been on Prednisone for nearly 2 years. Started on 20mg and have been slowly reducing and went down to 1mg on 1 March. In the last week I have developed really bad pain in my left shoulderblade and when I saw my doctor on Monday he increased my dose to 5 mg. I have taken 5mg Monday night, Tuesday morning and Wednesday morning but still haven t got any relief. How long would it normally take for the increased dosage to start being noticeable?