Details of Montgomery's ankle injury are unclear. Bears coach Matt Nagy addressed reporters prior to practice Wednesday and didn't offer any indication that Montgomery was hurt.
A rookie out of Iowa State, Montgomery has rushed 129 times for 466 yards and five touchdowns while serving as the Bears' lead running back this season. The Bears waived veteran running back Mike Davis last Saturday in a roster move that allowed them to recoup a 2020 compensatory draft pick. Without Davis on the team, Chicago's other options at running back are Tarik Cohen and Ryan Nall.
The Bears also listed tight end Trey Burton (calf), linebacker Danny Trevathan (left elbow) and linebacker Isaiah Irving (quad) on their injury report. Those three players didn't practice.
The Bears (4-5) play at the Los Angeles Rams (5-4) on Sunday, with kickoff set for 7:20 p.m.