Harden is unlikely to play in the team's remaining two regular season games, The Oklahoman reported Monday night.
Harden immediately fell to the court and stayed down while play was stopped for several minutes as referees separated Lakers and Thunder players who were arguing and a flagrant 2 determination was only made after the collision was reviewed on a video monitor at center court.
The league is still reviewing the situation and will not hand down punishment for World Peace on Monday.
Harden must pass a battery of league-mandated concussion tests to be cleared to play again, a process Oklahoma City says has already begun.
"Harden participated in a series of limited activities per NBA guidelines, but has additional steps that must be taken under the league-mandated concussion policy before he can make his return to the court," the Thunder said in a statement.
Despite being the Thunder's sixth man, Harden is a key part of the team's success. The third-year player is averaging 16.8 points, 4.1 rebounds and 3.7 assists for Oklahoma City which sits in second place behind the San Antonio Spurs in the Western Conference.
ESPNLosAngeles.com's Dave McMenamin and Ramona Shelburne and The Associated Press was contributed to this report.