The Cyclones say that Ejim, a preseason All-Big 12 pick and the league's top rebounder last season, is expected to miss 4-6 weeks.
Ejim's absence will be a huge blow for Iowa State to overcome during its non-conference schedule. The Cyclones will likely face No. 7 Michigan, BYU and Auburn without Ejim, who also led the Big 12 with 15 double-doubles last season.
Iowa State will open its season on Nov. 10 against UNC-Wilmington with just one returning starter, sophomore Georges Niang.