Giggs is due to have an X-ray this morning after colliding with Steve Sidwell in Wednesday's 1-1 draw with Aston Villa.
Pain game: Ryan Giggs is treated for his injury at Villa Park
The veteran winger was taken off clutching his right arm and United are praying that he has not suffered serious damage.
'It is very painful but hopefully he is going to be all right,' said boss Sir Alex Ferguson.
Giggs, who turns 37 later this year, has been superb again this season and shows no signs of slowing.
Action man: Giggs takes on Aston Villa's Fabian Delph
He is now a major doubt for the crunch Champions League clash with AC Milan on Tuesday.
That was expected to be a battle between him and David Beckham on the flank but Ferguson may now have to call in reinforcements.
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