The trio did travel to Saudi Arabia for the club’s mid-season training camp, however Howe revealed none of them have trained.
The Magpies play a behind closed doors friendly with Saudi Pro League leaders Al-Ittihad before flying back to the UK on Saturday.
Howe on Lascelles, Joelinton and Dummettt
Howe told NUFCTV: “The three who came off (at Leeds) haven’t trained and we don’t expect them to immediately.
“I’m not sure of the extent of the injuries. I think it’s one of those difficult ones to judge because we may need scans to determine that.
“And we haven’t had the luxury of doing that yet. “
Federico Fernandez ‘edging closer’
Meanwhile, Howe confirmed Federico Fernandez is edging closer to a return, but warned against rushing him back.
The Argentine injured his thigh in December - last featuring in the closing stages of the 1-0 win over Burnley at St James’ Park.
“He’s edging closer to returning to the group,” Howe said.
“He’s not quite there yet so this is a delicate stage with him. We want him back as quickly as possible but we don’t want to push him to where he has a setback.
“We’ve got to try and manage the next bit right.”