It leaves Pope in a race against time to make England’s squad for the European Championship, which starts in June.
The 31-year-old Pope sustained the injury as he dived to his left in an attempt to save a shot by Manchester United defender Sergio Reguilon that was blocked in front of the Newcastle keeper.
Howe said Pope will require surgery.
“The operation hasn’t happened yet,” Howe said, “but we’re thinking roughly around four months so it’s a big blow to us but one that we expected after the game.
“He’s naturally down because at this stage of the season where we have so many games, huge games coming up — he’s got, obviously, the Euros ahead of him as well, which he was determined to try to be involved in, and there’s still chance of that for him.”
Slovakia international Martin Dubravka will replace Pope, with Howe also having former Liverpool goalkeeper Loris Karius in the squad.
Newcastle have been linked with a move for former Manchester United keeper David de Gea, who is currently without a club, but Howe said no approaches have been made.
“We have not made any inquiries or any decisions about our recruitment leading into January,” Howe said.
“This is a chance for the goalkeepers we have at the football club to consolidate their positions, and that will be the same for every other position at the club.”
Defenders Sven Botman and Dan Burn and midfielders Sean Longstaff, Jacob Murphy and Harvey Barnes are among those currently missing because of injuries for Newcastle.
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