Kane has been in the Royal Rumble 19 times since debuting in 1996, so when he missed this year's, fans knew something was up.
Turns out Kane hasn't been on television since November 29, and he's been out of action for over two months, last appearing at a house show on December 5.
The Wrestling Observer Newsletter is reporting that Kane has been on the shelf, dealing with several nagging injuries. The Big Red Machine is pushing 50 now, and injuries don't heal as fast as they used to. No timetable has been given for his return, but it doesn't seem like they'd have a lot for him to do right now anyway.
You can watch his most recent televised match above, a victory over Luke Harper on the November 29 episode SmackDown.