Paterno was helped to his feet and eventually to the Penn State bench. His left leg was put in a brace, and toward the end of the quarter Paterno was taken off the field on a cart.
After the game, a university spokesman said he did not know the severity of Paterno's injury. The coach was flown home on a university plane, accompanied by Penn State's director of athletic medicine, Wayne Sebastianelli, and athletic director Tim Curley. He was expected to have X-rays taken tonight, with additional tests likely tomorrow.
Paterno was injured on a third and 2 from the PSU 28, when quarterback Anthony Morelli hit freshman tight end Andrew Quarless on a quick out. Quarless was knocked into Paterno's right leg, then Badger linebacker DeAndre Levy rolled into the coach's left leg. Replays showed Paterno's leg buckling backward at the knee.
In Paterno's absence, defensive coordinator Tom Bradley took over the head-coaching duties.
While sitting on the bench, Paterno attempted to stay involved in the coaching of the team. He was also spotted smiling at one point, not long before he left the field on the cart.
"He's a wily old rascal," Bradley told the Associated Press. "He's not going anywhere unless he has to. He's pretty tough."
Bradley also joked, "I told him he's not playing the low blocks like he used to."
Once Paterno left the field NCAA rules dictated that he no longer have headset contact with Bradley.
Bradley filled in for Paterno in the postgame interview room. The longtime Penn State assistant said there had not been any talk after the game about whether he would serve as acting head coach if Paterno is unable to resume his duties this week.
This is the second time this season Paterno has been injured following a collision with a player. In practice leading up to the Northwestern game, he was hit by Quarless, of all people. He was back on the sideline for the game against the Wildcats, though.
It is also the second time this season Paterno had to leave the field during a game. At Ohio State in September, he had to head back to the locker room twice due to an upset stomach.
Following that game, Paterno said he had never left the field during a game in his six decades as a player and coach.
The Nittany Lions fell to 6-4 overall and 4-3 in the Big Ten with the loss.