Ryan fell on Lehtonen in the Finnish crease with just over seven minutes left. Lehtonen left the game and was replaced by Petri Vehanen. There was no immediate word on the severity of Lehtonen's injury.
The Finns also lost to Canada in the round-robin tournament.
Canada tops Group A with 16 points, followed by the U.S. with 13 points and Finland with 12. If Finland beats Kazakhstan on Monday, it will again face the U.S. team in Thursday's quarterfinal.
Information from ESPNDallas.com's Mark Stepneski and The Associated Press was used in this report.