Rooney limped off at club training and was sent to hospital for scans, which could cast a shadow over his availability for the FIFA World Cup in Brazil.
It is not Rooney's first injury issue nearing a World Cup, with his latest issue digging up memories of a broken metatarsal that stunted his involvement in Germany eight years ago.
With United languishing in seventh position in the Premier League, interim manager Ryan Giggs will be unlikely to risk Rooney should there be any doubts about his fitness heading into Saturday's home clash against Sunderland.
There is a little over a month before England's opening clash with Italy, and they have already lost Theo Walcott, Kyle Walker and Jay Rodriguez to injury, while Andros Townsend is also out of contention due to an ankle problem.
