The Steelers placed NT Chris Hoke (neck) and RB Jonathan Dwyer (foot) on injured reserve on Thursday.
Hoke, an 11-year veteran, is one of the team's better run stoppers. The Steelers are 17-1 all-time when Hoke has started at nose tackle. Hoke was injured in Week Six and has been out of the lineup since. He had three tackles before being hurt.
Dwyer, a second-year back, had 16 rushes for 123 yards this season.
The Steelers signed LB Mortty Ivy and S Damon Cromartie-smith to replace Hoke and Dwyer on the active roster. Ivy has bounced back and forth between the team's practice squad and active roster and played in games against the Patriots and Ravens. Cromartie-Smith spent all of last season on the practice squad.