Bush had rushed for 411 yards and 5 touchdowns on 113 carries this season, complimenting star RB Matt Forte with his bruising and physical style of running.
He injured his ribs in the Bears' loss to the Vikings on Dec. 9 and was held out of their loss to the Packers last week. With the move, the Bears freed up the roster space to re-sign RB Kahlil Bell, who had appeared in two games for them earlier in the season.
However, Bell, at 5'11 220, will have a difficult time replicating the 6'1 245 Bush's ability to move the pile and fight for extra yards.
Chicago signed Bush in the off-season to a 4-year $14 million deal after he had spent the first four seasons of his NFL career with the Raiders.