The Dutch striker, 30, sustained the injury in the latter stages of United's 3-0 win at home to Olympiakos in the Champions League last 16 on Wednesday, in which he scored all of his side's goals.

"Following further investigation, Robin van Persie has a sprained knee, which will keep him out for around four to six weeks," United said in a statement on their official Twitter account.

The news rules Van Persie out of both legs of United's Champions League quarter-final against holders Bayern Munich next month and means that he may struggle to return to fitness before the end of the season.