England and Arsenal are in shock after Theo Walcott was ruled out for the rest of the season and the World Cup with a cruciate ligament injury.

The winger was carried off in Saturday’s FA Cup win over Tottenham after catching his studs in the turf and will miss six months with a ruptured anterior ligament in his left knee.

The news is a huge blow for England manager Roy Hodgson ahead of the World Cup in Brazil this summer.

Agony: Theo Walcott has been ruled out for six months with an anterior cruciate ligament injury

Clash: Walcott (left) sustained the injury in this challenge with Tottenham's Danny Rose

Blow: Walcott (left) will be out for the rest of Arsenal's season and England's World Cup bid

Walcott was booked in for a scan at 3pm yesterday, but early indications were that he had only strained knee ligaments, which would have ruled him out for six weeks.

It is understood Walcott did not show any telling signs of more significant damage in the hours after the injury. He was not in much pain as he was taken off the field, so there was genuine horror at the scan results yesterday.

Walcott will have surgery in London in the coming weeks before starting the long road back to fitness.

Arsenal team-mate Aaron Ramsey tweeted: ‘Gutted for Theo, he’ll come back stronger after this. Been fantastic for us so far this season. Have a speedy recovery mate.’

Controversial: Walcott provoked the wrath of Spurs fans while be carried off on a stretcher

Agony: Walcott is shown clutching his left knee, and it is now revealed he ruptured his cruciate ligaments

Per Mertesacker also took to social media, posting on Facebook: 'Theo, get well soon! We need you. Your BFG is always ready to carry you back on the pitch! All the best, mate!'

The forward had been hitting form after returning from an abdominal injury and played in a central role against Spurs because of the absence of first-choice striker Olivier Giroud and back-up man Nicklas Bendtner.

The injury means Walcott, 24, still waits to play in a World Cup despite being named in England’s 2006 squad as a 17-year-old.

He was not given a game in that tournament by Sven Goran Eriksson and was then controversially left out of the 2010 squad by Fabio Capello.

Hodgson is left with a problem on the right side of his team with Andros Townsend and Raheem Sterling still finding their way at international level. Daniel Sturridge is another option but he prefers playing down the centre.

Aaron Lennon has rarely shone for England while Adam Lallana and Danny Welbeck are normally deployed on the left.

Blow: Arsene Wenger will be without one of his star players for the remainder of the season

Arsenal will now step up their search for reinforcements up front. The Barclays Premier League leaders had already compiled a list of targets to take the burden off Giroud, although Wenger felt Walcott, Bendtner and Lukas Podolski could provide the  necessary cover.

Now injuries to Bendtner, who will miss at least a month, and Walcott have forced a rethink.

Wenger’s preference is to spend big on Bayern Munich’s Mario Mandzukic, Manchester City’s Edin Dzeko or Atletico Madrid’s Diego Costa.

But Arsenal accept that landing such a major player will be difficult in this transfer window and the alternative is to take Real Madrid starlet Alvaro Morata on loan until the end of the season.

Headache: Arsenal say Walcott is now out of contention for Roy Hodgson's England World Cup squad

On a more positive note for Wenger, Alex Oxlade-Chamberlain is on the verge of returning to action following his own serious knee injury.

The midfielder, who damaged his posterior cruciate ligament in Arsenal’s opening-day defeat by Aston Villa, returned to full training yesterday  and is set to make his long-awaited return for the club’s Under 21’s against Fulham on Thursday.

Meanwhile, centre back Thomas  Vermaelen is expected to resume training later this week despite picking up a knee injury against Spurs.

INSIGHT: MARK LEATHER (HEAD OF SPORTS PERFORMANCE AT BOLTON)

This sort of injury is one of the most serious a footballer can suffer, and is often one that takes the player by surprise, as seems to be the case with Theo Walcott.

It’s not unheard of for somebody to  suffer a cruciate ligament tear yet get through the game in which it happens. It’s only after, when the adrenaline stops, that the pain kicks in.

In Walcott’s case it looked as if his foot was on the ball but his balance was unstable and that forced his knee through a twist.

Sadly for Walcott, Arsenal and England, this isn’t something you can rush. Six months is often the best case if it is only the ligament that is torn — sometimes there is cartilage damage too and then you are looking at nine months to a year.

But given the age of the player and his value, trying to hasten the process for a World Cup could be a massive long-term risk.