UPDATE: The John Cena "injury" was scripted into the show, as well as the stretcher job. The stretcher used was actually put in place near the entrance ramp prior to the segment.
There was a fear that Cena did injure himself, due to his sell job, and while he may have tweaked the knee, it is nothing as serious that was played up on TV. The company pushed the medical update on the post game show as a way to drive attention towards the WWE Network.
ORIGINAL: In an update from last night, John Cena is not actually injured and was not taken to a medical facility last night. WWE played up the injury through out the show and post show, even showing footage where Cena said he heard the knee pop and the WWE doctor saying Cena was refusing an MRI. We'll have more on this shortly.