The defending Stanley Cup champions also assigned newly acquired forward Anthony Stewart to their AHL affiliate in Manchester on Tuesday.
Kopitar injured his knee shortly before the lockout ended in a collision while playing in Sweden. Kopitar has led Los Angeles in scoring in each of the last five seasons, and he shared the Kings' playoff scoring lead with captain Dustin Brown during last summer's run to their first championship.
The Kings acquired Stewart from Carolina last week for enforcer Kevin Westgarth. Stewart cleared waivers earlier this week.
Los Angeles put defenseman Matt Greene on injured reserve Monday with a back injury.