According to one report we received, Crowe and Kalisto were wrestling NXT Tag Team champions The Ascension when Crowe performed a head scissors takedown and injured his leg. The match was stopped and Crowe was taken to a hospital locally for testing.
Crowe joked the injury was "such a great birthday present" on Twitter. There's no word on how long he'll be out of action as of this writing.
Thanks to Jonathan Balofsky for his help.