An MRI exam on Monday confirmed the Kings' leading scorer will need corrective surgery that will keep him out indefinitely.
Kopitar broke his ankle when he fell awkwardly during the Kings' victory over Colorado last Saturday. Coach Terry Murray said the Slovenian All-Star will be out for at least six weeks, sidelining him until well into the postseason.
Kopitar leads the Kings with 25 goals and 43 assists in 75 games.
Los Angeles also lost second-leading scorer Justin Williams last week to a dislocated shoulder that will keep him out until the playoffs, and possibly longer.
Los Angeles is in a fifth-place tie with Nashville in the West.