On Monday, team officials confirmed the tear, first reported by ESPN's Adam Schefter.
Coach Ron Rivera said Stewart will be re-evaluated in 10 days. He didn't rule out a return for the season finale at Atlanta in three weeks or a possible first-round playoff game.
But Rivera was adamant Stewart would not play on Sunday against the New York Jets and indicated the following week's rematch against New Orleans was doubtful.
Stewart was hit in the knee by New Orleans' Keenan Lewis at the end of a 16-yard reception and run. He did not return to the game, but did return to the sideline with the knee wrapped.
While the hit was legal, Rivera expressed concern for a growing number of knee injuries with defenders lowering their hit zone to avoid hits to the head and neck area that the league is cracking down on.
"If you go back and look at our situation, we've had a number of MCLs and ACLs,'' Rivera said the day after Carolina (9-4) saw its franchise-record eight-game winning streak end. "My big wonder is that a trend in the league now? Is the concern about the hits to the head such a big thing that the targets are being lowered?
"That's something that's probably going to have to be looked at as far as the league is concerned to see what is happening and what can we do to help protect these guys.''
Rivera said fining such hits is not the solution.
"That's hard,'' he said. "We have lowered the strike zone. It's kind of like the strike zone [in baseball]. The pitchers are getting squeezed big-time. Now the tacklers are getting squeezed. It's just unfortunate. And hopefully, there is a solution out there and hopefully during the offseason the league will get a chance to look at that and see if they can rectify that.''
For Stewart, this is yet another setback in several seasons of disappointment. He was placed on the physically unable to perform list before this season to recover from offseason surgery on both ankles. He returned after missing the first eight weeks.
Rivera said Williams, who leads the team with 662 yards rushing, again would carry the load instead of splitting carries three ways.
"I will be mostly about DeAngelo,'' he said. "It will be interesting how he reacts.''
Meanwhile, the Panthers might get right guard Chris Scott back after missing five games with a knee injury. Scott started seven straight games before the injury.