"He should be out for three weeks, maybe a month at most," United coach Alex Ferguson said.

"It has been bothering him for a few weeks, so we sent him to a specialist in London and he had an injection.

"We have been considering what we should do about it. The best thing is to get it treated and out of the road now because everyone in the squad is fit."

Carrick made just one substitute appearance in United's first three Premier League games.

He is expected to miss matches against Liverpool and Everton as well as the Champions League group-stage game against Scottish giants Rangers.