The team made the announcement on Tuesday. Timonen's return to the ice is uncertain.
The 39-year-old Timonen signed a one-year contract this summer for $2 million. He has been Philadelphia's top defenseman for several years.
Timonen has spent the last seven seasons with the Flyers after playing his first eight with Nashville. He has 571 career points on 117 goals and 454 assists. Timonen is plus-38 for his career.