From ESPNChicago and the Chicago Tribune, Bears’ Running Back Matt Forte underwent surgery on his left knee very recently. 
Forte apparently suffered a MCL sprain during a Bears victory in September against Seattle. This injury was reason for the lackluster running game in Chicago according to former offensive coordinator Ron Turner.
After his rookie season where rushed for over 1,200 yards, this year Forte managed 929 yards rushing. He averaged 3.6 yards per carry.