An MRI revealed a slight sprain of the MCL, coach Travis Green said Saturday.
"It's not too bad," Green said. "We'll have our doctors re-evaluate him when he gets home. It was probably as good of news as we could receive."
Pettersson may be able to return within two weeks. The 20-year-old rookie forward was named to the All-Star Game, scheduled for Jan. 26, on Wednesday.
"I don't want to put a timetable on it but that's usually what these are," Green said.
Pettersson did not play in a
5-0 loss at the Toronto Maple Leafs
on Saturday. He was injured in the second period of a 2-0 loss at the Montreal Canadiens on Thursday.
"I'm walking fine. I feel better today than yesterday, so that's good," Pettersson said Friday in remarks tweeted by the Canucks.
Pettersson's legs got twisted with Montreal forward Jesperi Kotkaniemi's at 5:44 of the second period Thursday.
"Two guys who get tangled," Green said after that game. "I've watched it a lot of times. First of all, it's not a dirty play by their player at all. He gets hooked a little bit, [Pettersson] actually pushes back on him and leans back and probably tries to give him a little bit of a reverse hit, and two young guys fall to the ice."
Pettersson leads NHL rookies with 42 points (22 goals, 20 assists) in 38 games. He was NHL Rookie of the Month in October and December.
"I think we both just fell down and I maybe fell on his leg," Kotkaniemi said. "I'm not sure what happened. ... I don't want to hurt anyone. I said this morning that he's a good player, so everyone in the League wants that he's on the ice, so so do I."
Pettersson broke a Canucks record held by Pavel Bure with his seventh game-winning goal of the season Wednesday, completing his first NHL hat trick in a 4-3 overtime win at the Ottawa Senators.
"It's not good that he's out, but as long as he's not out too long, it's part of the game," Green said Thursday. "You do have bumps and bruises along the way, and a lot of teams have to play without some of their top players."
NHL.com staff writer Mike Zeisberger and correspondent Sean Farrell contributed to this report
