He is expected to need 12 weeks of recovery, so he will likely miss all or most of training camp and the NHL pre-season. Montreal's first game of the regular season is on Oct. 7 in Toronto against the rival Maple Leafs.
The injury occurred on Thursday. The team gave no other details of the injury other than that it will not require surgery.
Pacioretty plays on Montreal's top line. The 26-year-old led the team with 37 goals and a career-high 67 points last season and added another five goals and two assists in 11 playoff games. It was his second straight season with more than 35 goals.