"He's (Benteke) got ligament damage which will keep him out for a minimum of six weeks," Hodgson told a news conference. "We don't think he'll be able to train for six weeks."
"Loftus-Cheek has a thigh strain which he's been battling with for some period of time, which will keep him out of the game.
"Unfortunately, at the moment we've been hit by a plague of injuries at a time when we could have done without it."
James Tomkins' illness leaves Palace short-staffed in defence, while Benteke's back-up striker Connor Wickham is still weeks away from returning from his own knee injury.
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Palace are rooted at the bottom of the league standings having lost the first six games without scoring and Hodgson concedes there could be more suffering ahead for his side.
"Manchester United have a very strong squad but we will be looking to give them a good game and hope for any good luck that is around," he added.
"There could be more pain ahead, with the likes of Manchester United and Chelsea, but we wont be fazed as we work on our task that we have ahead of us as a group."
United have made an unbeaten start to the campaign and have not lost to Palace in the top-flight since May 1991.
(Reporting by Hardik Vyas in Bengaluru; Editing by Keith Weir)
