Pittsburgh Steelers quarterback Ben Roethlisberger insisted he would be "fine" after hurting his knee in a win over the Dallas Cowboys.

Roethlisberger, 38, left the field before half-time during the Steelers' 24-19 NFL victory on Sunday after a suspected knee injury.

But the star QB had no doubt he would be okay after helping the Steelers improve to 8-0 for the first time in their history.

"No, I'll be fine, thank you for asking," Roethlisberger told reporters.

He earlier said: "Someone hit me right in the side of the knee, it felt like it kind of bent my knee a little bit.

"It's part of the game of football, guys get hit all the time, I just had some discomfort so we thought at the end of the half we'll head in and get it looked at.

"Doctors wanted me to keep them updated in the second half so I was just keeping it loose and keeping it warm."

Roethlisberger joined Tom Brady as the only QBs in NFL history to lead their teams to an 8-0 start at age 38 or older (must have started all eight games).

He completed 29 of 42 passes for 306 yards and three touchdowns, including connecting with JuJu Smith-Schuster and Eric Ebron as Pittsburgh scored 15 unanswered points in the fourth quarter.

"I'm just really proud of the way the guys fought and just played good football," Roethlisberger said.

"We didn't do what we wanted to do, we didn't control the ball, we didn't convert on third downs a lot, but we found a way to win.

"We've got to stop playing so ugly on offense, but it [Dallas] is a good team."