A couple of days later and the Chiefs announced that he had been waived. The technical designation was waived/injured.
Like Brad Cottam, a few weeks ago, the Chiefs technically had to waive him before he could be placed on injured reserve.
This is a procedure done in the NFL to basically stop teams from "stashing" young players on IR. So if you have a player who is not a vested veteran (less than four years of service), he must be sent to the waiver wire, pass through without anyone claiming him and then his rights are returned to the Chiefs.
So Johnson is now on IR along with Brad Cottam and Chandler Williams (from 2009).