General manager Jim Rutherford made the announcement Monday. According to coach Mike Sullivan, he suffered the injury during practice on Friday. There is no timetable for his return.
The Penguins say Crosby sat out a preseason game Saturday against Columbus because he wasn't feeling well and missed practice Monday to undergo concussion testing. They added that Crosby's status will be updated when more information becomes available.
Pittsburgh opens the regular season Thursday at home against the Washington Capitals.
The two-time Stanley Cup champion and reigning Conn Smythe Trophy winner missed significant time earlier in his career with concussion problems. The 29-year-old Crosby was the playoff MVP last spring, leading the Penguins to their fourth Cup in franchise history.
Information from The Associated Press was used in this report.