Leicester Tigers flanker Lewis Moody said he was "devastated" to be missing the rest of the season through injury and England's tour of New Zealand.
A ruptured right Achilles tendon forced the openside off during England's RBS 6 Nations opener against Wales at Twickenham on February 2 and he has not played since.
Moody is in Umea in Sweden where a tendon specialist has revealed the full extent of the damage.
He said: "The specialist told me I'm going to be out for 16 weeks, which means I won't play for the rest of the season. I'm absolutely devastated.
"I've had my Achilles scraped, which is basically where all the loose scar tissue is cleared out. I've got a 50% rupture of the tendon.
"I'm really, really disappointed, not so much because I'll miss England's tour to New Zealand this summer but because the Tigers are in the EDF final, and I can't imagine them not also being in the League final too. Every game you miss is a game you can never get back."
He added: "The only good thing about this is that I get to spend more time with my wife Annie and my baby son Dylan, who was born earlier this month."
A shoulder injury, which also required surgery, sidelined Moody from last year's RBS 6 Nations too.
He went on to play a key role in England's 2007 World Cup campaign, which saw them lose to South Africa in the final.
Dr Hakan Alfredson, a world expert on tendon injuries, met Moody and representatives of the England and Leicester medical teams in Sweden on Thursday.
It was decided that an operation was required, and the procedure took place on Thursday afternoon.
England head coach Brian Ashton said: “I am bitterly disappointed for Lewis.
“I hope the operation has been successful and that he is playing in his usual combative way as soon as possible.”
Leicester forwards coach Richard Cockerill added: “We are very disappointed for Lewis.
“He is an important player for us, so it’s obviously a blow for the club.
“We wish him well in his recovery and look forward to seeing him back in a Tigers shirt once he is ready to play again.”