The club sent Johnson to America earlier this week where he was operated on by the man credited for saving the careers of Alan Shearer and Michael Owen - world-renowned surgeon Dr Richard Steadman.

Fulham boss Roy Hodgson had hoped the striker would return to action before the season's end but his worst fears were confirmed this afternoon.

A statement on Fulham's website read: "The club can confirm that following knee surgery in Colorado by eminent specialist Dr Richard Steadman, Andrew Johnson will not be available for the remainder of the current 09/10 season.

"Following the prognosis received from the surgeon, the Club fully expects Andrew to take part in the latter part of pre-season training in readiness for the new season."

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Johnson's season has been plagued by injury. The 28-year-old's first setback came during the opening weeks of the season when he dislocated his collarbone during a Europa League qualifier with Russian side Amkar Perm.

The former England man made a quick recovery but was soon in the treatment room again after suffering a groin injury which ruled him out for another three months.

He made his long-awaited return in Fulham's 2-1 defeat at Chelsea just after Christmas but only played three more games before this latest setback.

The news comes as a particularly bad blow for Fulham manager Hodgson, whose striking options have been reduced by injuries to key forwards recently.

Clint Dempsey is out until April and Zoltan Gera, who filled in up front in Johnson's absence, is also struggling with a knee injury.

Bobby Zamora has only just returned from a collarbone injury while Erik Nevland, David Elm and new signing Stefano Okaka have only played a handful of games between them.

Hodgson admitted following Wednesday night's win over Portsmouth that he feared Johnson's season could be over.

"There is a risk that he will be out for the rest of the season, but there is also some optimism," the former Inter Milan boss said.

"However, the experience of our medical people think it might be (season-ending).

"I am disappointed in that, because I was still believing he was going to come back and it would not be that long.

"Now I may be looking at the rest of the season with a limited and inexperienced group of front players."

Much pressure is now likely to fall on the shoulders of 20-year-old Okaka, who signed on loan until the end of the season from Roma on deadline day.

Hodgson has admitted that the youngster will take time to adjust to English football but also stated that he believes the squad will be able to survive without Johnson.

Hodgson said: "If we struggle up front then we'll have to re-arrange our team. Dempsey is not out for the rest of the season, if we get him back that will solve a lot of problems, (Simon) Davies won't be out for so much longer and neither will Gera."