What Causes Light And Prolonged Period After Having Cortisone Shot?

I m a 42 yr old women, recently diagnosed with a labrel tear in my right hip. I received a cortisone shot on Feb. 27 and exactly 1 week later (Mar. 6) my period arrived. I m usually on a 26 day cycle. Normally, my next cycle should have arrived on Mar 19. So far, this extremely light period has been going on for 9 days straight. Is this due to the cortisone shot I received?