Gilbert reached a deal with the Nuremberg Ice Tigers of Germany's DEL on Friday, theScore reports.
The Kings traded Gilbert to the Capitals on Wednesday for a conditional fifth-round draft pick in 2017, and he'll start out with AHL Hershey.
Gilbert was placed on waivers Wednesday, Elliotte Friedman of Sportsnet reports.
Gilbert hasn't dressed in 11 straight contests and has seen action in just nine of the Kings' last 20 games since returning from a three-game suspension in November.
Gilbert has served his three game suspension, and is eligible to return to the Kings' lineup for Thursday's game against the Canadiens, TSN 690's Amanda Stein reports.
Gilbert was suspended by the league for three games on Thursday for boarding Nick Ritchie during a 4-0 loss to the Ducks on Tuesday night, Stephen Whyno of the Associated Press reports.
Gilbert picked up an assist while skating 15:06 during Thursday's 4-3 overtime victory in Dallas.
Gilbert was benched for Friday's home game against the Flyers, NHL.com reports.
Gilbert (knee) signed a one-year, $1.4 million deal with the Kings on Friday.
Gilbert had surgery on his left knee Wednesday and is expected to need six months to recover.