Pope hurt himself while diving to make a save seven minutes from time at St James’ Park and had to be replaced.
Howe, who is already dealing with a lengthy injury list, told TNT Sports: “It’s a massive blow for us if Nick is going to be out for any length of time.
“It’s usually the way. It looks really innocuous but they look the most serious ones at times. You could see his distress, I think he’s dislocated his shoulder just diving.
“The arm kept going and it looks like we could lose him.”
Anthony Gordon scored the only goal for Newcastle to secure a deserved win against Manchester United. It was the in-form winger's seventh goal of the season.