Chara was injured in the first period of Wednesday's 6-3 loss in Colorado. The Bruins said he will be re-evaluated after four weeks,
The 41-year-old Chara is the sixth Bruins defenseman to go down with an injury.
The Bruins were already without defensive stalwarts Charlie McAvoy (concussion), Kevan Miller (broken hand), John Moore (lower body) and Brandon Carlo (upper body), as well as rookie Urho Vaakanainen, who sustained a concussion last month after being called up to fill in.
"It seems like we're losing a guy every game," goaltender Jaroslav Halak said. "We need to keep playing hard, and whoever comes in the lineup has to step up."
The Bruins also said Moore and center Patrice Bergeron (upper body) would travel back to Boston to be re-evaluated by team doctors. The Bruins continue their road trip on Saturday at Arizona before going to Detroit on Wednesday.