A win would guarantee England progression into the quarter-finals as group winners, while Scotland need to beat England by an eight-point margin to have a chance of qualifying.
Armitage expects a Scotland backlash after their narrow loss against Argentina on Sunday.
"We know how Scotland will come at us. Every year they come and try and turn us over," said Armitage. "We will be ready for it.
"It is going to be massive, the biggest game of my career."
Matt Stevens and Nick Easter are both fit for the clash after recovering from injury.