The defending Stanley Cup champions made the move Monday before travelling to Dallas to face the Stars on Tuesday night.
Penner missed the Kings' past four games with a lower-body injury after getting hurt March 31 in Dallas. The eight-year NHL veteran has two goals and nine assists in 25 games this season.
The Kings began Monday in a third-place tie with Vancouver in the overall Western Conference standings. Los Angeles trails Pacific Division-leading Anaheim by nine points after Sunday's 4-3 shootout loss to the Ducks.
This is a great day for me. This is something I've been thinking about for a long time. This is a great opportunity that the St. Louis Blues organization, (owner) Tom Stillman and Doug Armstrong are giving me and trusting me in doing...This is going to be a great challenge for me.
— Martin Brodeur, after announcing his retirement as an NHL player and becoming a senior adviser with the Blues on Thursday