Everton striker James Vaughan has flown to the United States to see renowned knee specialist Dr Richard Steadman after his latest setback.

"The knee just locked a couple of times in training and it is terrible luck for the boy," said Toffees manager, David Moyes.

Vaughan has suffered a host of injury problems since announcing his arrival with a debut goal against Crystal Palace - handing him the record as the Premier League's youngest goalscorer.

He has endured knee injuries before as well as missing large parts of the current season with a dislocated shoulder.

"We don't know yet whether it is the same problem as before but it is the same knee," said Moyes.

"We decided he should have the operation now rather than wait until the end of the season and he has to be a doubt for the rest of the campaign."