To make room on the roster, defenseman Stephane Robidas was placed on IR retroactive to Dec. 19.
Lehtonen, 28, is 13-4-1 with a 2.35 goals-against average and a .926 save percentage in 19 appearances this season. His 13 wins led the NHL at the time of his injury.
Robidas, 34, missed the last three games after suffering a lower body injury against the Anaheim Ducks on Dec. 19. He has recorded 11 points (2 goals, 9 assists) in 32 games this season.
The Stars host the Columbus Blue Jackets on Thursday.