Maxwell said he had no idea if he would miss any weeks due to the injury.
"To be honest, with ankles sometimes it can look really bad and it can turn out all right and sometimes it can look OK and end being really bad," he said.
"I actually have no idea.
"It's different to the one I did earlier in the year - same side but different injury."
Maxwell's injury is a further blow to the out-of-form Magpies, who have lot four of their past five matches and are in danger of slipping out of the eight.
After a rest this weekend, the Pies face 10th-placed Adelaide at the MCG in two weeks, with the Crows one win behind Collingwood.
"(The bye has) probably come at a good time for us, a lot of the guys are down on confidence," Maxwell said.
"The team hasn't changed in terms of the talent we've got on our list, and the availability we have of players.
"The guys are just down on confidence and I think we've seen that a lot of teams been written off at different times during the year and have bounced back because they get their confidence back and they start believing in each other a bit more."
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