Matheson underwent an MRI on Wednesday to determine the extent of his lower-body injury.
The 28-year-old blueliner was acquired from the Pittsburgh Penguins on July 16 in exchange for Jeff Petry and Ryan Poehling.
With Matheson on the sidelines, Corey Schueneman was recalled from the AHL's Laval Rocket.
Schueneman, 27, played 24 games with the Canadiens last season. He registered two goals and four assists.
Updated, Oct. 13, 7:53 p.m.:Following the results of his MRI, Matheson is expected to miss eight weeks with an abdominal muscle strain, the team announced on Thursday evening.
