An MRI revealed a full tear to his MCL and at least a partial tear to his ACL. He will need a minimum of four to six weeks to recover, team trainer Rick Burkholder said, though major knee surgery may be needed.
Kelce was carted off in the third quarter of the 24-23 victory over the Baltimore Ravens.
Coach Andy Reid said Monday a designated injured-reserve spot is available for Kelce if the Eagles decide it is necessary, which would allow the second-year player out of Cincinnati to be put on IR for eight weeks before returning to the active roster.
Offensive tackle King Dunlap, who also left Sunday's game in the third quarter with a sore hamstring, likely won't practice Wednesday and is day to day, Reid said.
Despite a makeshift line blocking for him Sunday, Michael Vick didn't take as many hard hits as last week and was sacked only twice. He scrambled eight times for 36 yards before kneeling twice at the end.
Jackson is sore with a hamstring spasm he suffered before Sunday's game, and Maclin has a bruised hip on top of a previous injury, Reid said.
Information from The Associated Press was used in this report.