What Causes Severe Pain In Knee After Taking Cortisone Injection?

I have been suffering from knee pain since October of this year. I had a cortisone injection & since that day my knee got worst. Also I had fluid removed three times. I am being followed by a rheumathologist which I am on different medication but I see no improvement. My knee is very swollen both knees but the one that I have the most problem is my left knee. I went for an MRI last week still waiting for my doctor to give me my results I did this at a private clinic.
I am not sure what else to do please let me know if you have any advise for me.
Thank-You