Second-year linebacker Nick Kwiatkoski is expected to take Freeman's spot in the starting lineup against the Tampa Bay Bucs on Sunday. Chicago also elevated third-year linebacker Jonathan Anderson to the active roster Tuesday.
Losing Freeman for the year will be tough for the Bears to overcome. The 31-year-old linebacker led the team with 110 tackles last year -- despite being suspended four games for violating the league's policy on performance-enhancing substances.
Freeman was credited with a team-high 10 tackles against the Falcons on Sunday.
After spending four seasons in Indianapolis following a three-year stint in the CFL, Freeman signed a three-year, $12 million deal with the Bears with $6 million in guarantees in the spring of 2016. There is no guaranteed money left on Freeman's deal for the 2018 season.
He was voted one of the Bears' team captains before Sunday's game.
Chicago also signed wide receiver Tanner Gentry to the active roster from the practice squad, and released receiver Rueben Randle from injured reserve.
Gentry -- an undrafted rookie out of Wyoming -- had four catches for 77 yards and one touchdown in the preseason.