After his injury on this week's WWE Raw, John Cena announced on Twitter that he will undergo an MRI on his left knee tomorrow:
I am headed to grand rapids right now for early morn MRI on left knee. @wwe no matter what the result, I will be in the ring tomorrow!
— John Cena (@JohnCena) November 20, 2012
Cena is still advertised to appear at tomorrow's Smackdown tapings, for which we will have full coverage.