Bulls missing four starters for game against Bucks
Coach Tom Thibodeau did not mention Noah's injury during his pregame availability, but the Bulls announced the injury a short time later.
Noah is averaging 9.4 points and a team-high 8.8 rebounds. He started each of Chicago's first 18 games.
Luol Deng (left calf tightness) and Jimmy Butler (sprained right big toe) already had been ruled out for Tuesday night's game. Derrick Rose is likely out for the season after right knee surgery, making Carlos Boozer the only starter against Milwaukee who also started on opening night at Miami.