Fiorentina forward Giuseppe Rossi will be out for four to five months after undergoing another operation on his right knee.

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A routine examination on a muscular injury Rossi, 27, picked up recently revealed that the knee which was operated on last January was showing signs of having been overburdened and he was sent to visit specialist knee surgeon Dr Richard Steadman's clinic in Colorado -- who had done his previous operations.

A statement on the Fiorentina website read: "Fiorentina announces that Giuseppe Rossi was today submitted for surgery on his right knee in Colorado. Examinations showed a good stability to the cruciate ligament previously operated on. Resumption of activity will be dictated by the specialist, which is estimated at around four to five months.''

Rossi underwent surgery for the second time in January, but despite returning for the final few matches of last season, he was not considered fit enough to appear at the World Cup by then Italy coach Cesare Prandelli.

The forward, who was born in the United States and played for Manchester United, has had a succession of knee injury problems that have blighted his career to date.