Hossa was injured Saturday night during Chicago's 5-1 victory over the Pittsburgh Penguins outside at Soldier Field. It is unclear exactly when Hossa got hurt, but he took a hard hit from Penguins forward Craig Adams during Chicago's second power play of the first period.
The announcement on Monday is a big blow for the defending Stanley Cup champions, who lead the NHL with 213 goals this season. Chicago is competing with St. Louis and Anaheim for the top spot in the Western Conference. The Blackhawks and Blues also are tied for the Central Division lead with 86 points apiece.
The 35-year-old Hossa has 24 goals and 26 assists in 57 games. He needs 15 points to reach 1,000 for his career.
Brandon Saad moved up to take Hossa's spot on the right side of Chicago's top line against the Penguins. Blackhawks coach Joel Quenneville also could put Patrick Kane back together with centre Jonathan Toews, but that move would weaken the scoring depth on the Blackhawks' lines.
Hossa's absence likely means more playing time for Peter Regin, who was scratched against Pittsburgh.
"There's going to be some quality ice time shared amongst the guys," Quenneville said after practice on Monday. "I thought Saader did a real good job getting put up on that line there as the game progressed the other day so we'll probably put him there and we'll get Peter back in the lineup."
The 21-year-old Saad has a career-high 18 goals and 23 assists in his second full NHL season.
Quenneville also indicated Hossa's injury likely won't affect how the team approaches Wednesday's NHL trade deadline.
"I think we're fine," he said.
Also Monday, the Blackhawks announced they agreed to a three-year contract extension with forward Brandon Bollig that runs through the 2016-17 season.
The 27-year-old Bollig has a career-high 12 points (six goals, six assists) in 62 games. He leads the team with 138 hits and 69 penalty minutes.
"Beyond excited to remain a Blackhawk for the next three years," Bollig said on Twitter.