The injury did not occur from one incident but built up over several years, sources told ESPN.
Vault, who was entering his senior season, has a redshirt available and plans to return in 2018. He was projected to start at wide receiver and returner in 2017.
Vault had 15 receptions for 164 yards and two touchdowns last season while adding 560 yards and a touchdown on kick returns. The converted running back has four career kick return touchdowns and averages 26 yards per return, earning third-team All-Big Ten honors in each of his first three seasons. He also has 32 career receptions and 82 career rushes.