Cristiano Ronaldo today underwent a successful operation on his right ankle, Manchester United have announced.
The Portuguese winger had a procedure in Amsterdam carried out by a Dutch surgeon, but the club say they will not be able to state when he will be fit again until he is seen by the specialist in a month.
It is likely he will be out for at least six weeks and miss the start of the new season.
United said in a statement: 'Cristiano Ronaldo underwent surgery today to his right ankle.
'The operation was performed by Professor C. Niek van Dijk at The Academic Medical Centre in Amsterdam and the initial indications are that the procedure was successful.
'Cristiano will begin his convalescence under the direction of club medical staff and an estimation of his return to full fitness will be possible following review by the specialist in one month.'