Ralph was injured while fighting for a rebound and was helped off the court with 5:18 left in the first half.
She had 11 points and six assists, and No. 2 UConn was leading 39-34 at the time of the injury.
Ralph, last year's Final Four MVP, has had two operations on her left knee and was red-shirted for her sophomore season.
Ralph is averaging 9.7 points and 5.6 rebounds.