The France international was injured in Friday's season-opening 3-1 victory over Hoffenheim, his first Bundesliga match since a previous ligament injury to the same left leg in February that also ruled him out of the World Cup in Russia.
"Coman will require surgery and will be out for several weeks," Bayern said in a statement after the 22-year-old Frenchman was injured shortly before halftime following a rash challenge from Hoffenheim's Nico Schulz.
Fellow winger Serge Gnabry, who along with Coman are regarded as successors to veteran wide men Franck Ribery and Arjen Robben, is also nursing a muscle injury.
Bayern are once again strong favourites for the league title, having won the last six.
(Reporting by Karolos Grohmann; Editing by John O'Brien)
