The sophomore was helped off the field after he served as a blocker on a kickoff return in the Nittany Lions' 31-20 win over Indiana at Beaver Stadium Saturday.
Monday, Penn State announced that Beachum sustained a torn ACL in his right knee. He will have surgery within the next two week, according to the release, and is then facing a rehab of at least nine months.
The Youngstown native played as a true freshman last year and has seen action in every game to date this season.
He has a redshirt available for 2010 if needed.
Beachum ranks fourth on the team in rushing this season with 113 yards and a score on 24 carries.