Ristolainen has already missed the past three games due to the injury.
The 30-year-old from Turku, Finland, has 19 points (four goals and 15 assists) in 63 games with the Flyers this season. He is also fourth on the team in average ice time with 20:31 minutes per game.
He was named to Finland’s roster for the 4 Nations Face-Off but did not play in the tournament due to injury.
The Flyers (28-33-8) are last in the Metropolitan Division and have lost eight of their last 10 games.
