The 27-year-old big man had been selected as a starter for the 2018 NBA All-Star Game.
The four-time All-Star was also putting up MVP-caliber numbers with 25.2 points, 12.9 rebounds and 5.4 assists per game.
On Friday, Cousins registered 15 points, 13 rebounds and 11 assists.
Teammate Anthony Davis tweeted the following regarding the injury:
Davis and Cousins have formed one of the NBA's best duos this season, leading the Pelicans to a 27-21 record, which is good for sixth in the Western Conference.
The injury comes at an especially bad time for Cousins, since he is set to hit free agency during the offseason. He was a near lock to land a max deal, although he may still do so.
While Cousins will miss the remainder of the 2017-18 season, which severely damages New Orleans' playoff aspirations, he has a chance to return in time for the start of the 2018-19 campaign provided he doesn't need the full 10 months to recover.