WWE posted an injury update on Christian last night, saying that he re-aggravated a prior neck injury during the fight with WWE Champion CM Punk on last night's RAW Supershow. As noted before, Christian has been pulled from WrestleMania 28 and replaced on Team Johnny by Drew McIntyre.
WWE's report adds the following: "Although Christian claimed to also have experienced ankle pain following the onslaught, doctors later confirmed he did not re-aggravate the ankle sprain he suffered last year while on tour in Europe."
However, F4Wonline.com reports that Christian was pulled from WrestleMania because his ankle is not 100%. When WWE put the match together, they thought Christian would be ready to go but he's not.