Can Cortisone Injection In Knee Result In Early Menstruation?

I had a cortisone injection in my knee last Thursday. Today (Monday) I started my period - again. I just had it 2 weeks ago. I always start 28 days after the day I started the month before so I am very regular. Could the cortisone shot have been the cause? What should I do? If this is a normal reaction, how do I get my cycle back to normal?