They also assigned forward Brian Boyle to the Manchester Monarchs of the AHL.
Johnson, who turned 22 on Tuesday, was hurt Oct. 12 and underwent shoulder surgery later that month.
Before the injury, he played in two games, with no points and two penalty minutes. Last season as a rookie, Johnson had three goals, eight assists and 96 penalty minutes in 81 games with the Kings.
Los Angeles opens a three-game road trip in Dallas on Saturday night.