Owen has flown home after rupturing his anterior cruciate ligament in the second minute of Tuesday's 2-2 Group B draw with Sweden in Cologne.
In a column signed by Owen in The London Times, the striker said: "My best wishes go with the rest of the lads but I won't be playing competitive football again in 2006.
"No one can predict exactly how long I will be out with a ruptured cruciate ligament in my right knee but it probably means at least six months.
"When I didn't get up, my family knew it was serious and they were waiting for me by the dressing-room.
"My mum, wife and sister were obviously upset seeing me lie there with my knee swelling up like a balloon but I do have the ability to be quite philosophical about these things.
"I have been called cold in the past and, at times like this, it is a real strength."
Owen's absence is a major blow to England's prospects at the finals, even though he had been short of his best form following a prolonged recovery from a broken foot suffered on Dec. 31.
WINNER'S MEDAL
Yet the 26-year-old remained buoyant about his team mates' chances as they prepare for Sunday's second round game against Ecuador in Stuttgart.
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"My tournament might be over but I still want that medal around my neck."
Owen's injury is also a bodyblow for his club, Newcastle United, who paid Real Madrid 16 million pounds ($29.47 million) for him last August and who have had little return.
The striker missed the early stages of their campaign with a hamstring problem. Coupled with the broken foot, he made only 10 starts in 2005 and one substitute's appearance in 2006.
"I can control my emotions and I can honestly say that when I was flat on my back with ice-packs around my knee, it wasn't self-pity I was feeling but guilt," Owen said.
"I was sending text messages apologising to all sorts of people for letting them down.
"I feel really guilty when I think of the people at Newcastle United.
"I think of the chairman, Freddy Shepherd, who has invested all that money, and Glenn Roeder, the manager, who has kept in touch through the tournament and been very supportive.
"And those great fans who have only seen me for 11 matches."