Hills, a true freshman, injured the leg during Saturday's game against North Carolina after throwing an interception in the second quarter. Hills couldn't put any weight on the leg after the injury.
Hills' knee was "extended and bent backward when he tried to make a tackle."
Prewitt tweeted that Hills "went into the locker room ... begging trainers to tape him up and let him return."
Hills, out of Pittsburgh's Central Catholic High School, has completed 57 percent of his passes this season. He's 97 for 169 for 1,336 yards, eight touchdowns and seven interceptions. He's been sacked 24 times this year.
Hills has started every game this season after Maryland lost quarterback C.J. Brown to injury. Brown tore his ACL during preseason workouts.
Maryland is 4-3. The Terrapins will travel to play Boston College on Saturday.