Hightower is scheduled to have an MRI exam Monday, reported The Washington Post. Hightower told The Post he didn't know how serious the injury was but that he is "determined to come back" this season.
Hightower injured the knee when it buckled during a 4-yard run in the third quarter. He was helped off the field while putting almost no weight on the leg, then carted to the locker room from the sideline.
It had been a productive day for Hightower before he exited, with 88 yards rushing on 17 carries.
The Associated Press contributed to this report