The forward sustained the injury with 4:15 remaining in the second period of the Flyers' 4-1 loss to the Colorado Avalanche at Wells Fargo Center on Monday.
He is expected to be sidelined until at least the third week of November.
"You lose any player and it's not a positive or our hockey team," Flyers coach Dave Hakstol said. "[Raffl has] played good hockey for us. And if he's going to be out for a little while than somebody else is going to have to step in and do a good job. Injuries are part of the game. That's the unfortunate thing. ... But hope the best for [Raffl] here."
Raffl has two assists in nine games with Philadelphia this season, and has 116 points (64 goals, 52 assists) in six NHL seasons, all with the Flyers.
Philadelphia's next game is against the Boston Bruins at TD Garden on Thursday (7 p.m. ET; SN360, TVAS, NESN, NBCSP, NHL.TV).
