In what has become a familiar theme for Paula Radcliffe, the women’s marathon world record-holder revealed last night that she is a doubt for the World Championships in Osaka, Japan, this summer. Since 2002, Radcliffe’s all-conquering year, she has made it to the start line of only two “major” championships through a combination of injury, illness and childbirth.

Radcliffe, 33, dismissed any suggestion that her career may be in decline, insisting that every decision she takes this year will be made in her best interests for the Beijing Olympics next year. She has been forced to stop running with a stress fracture to the left of her sacrum (at the base of the spine), which, she said, would be scanned in three weeks’ time.

Linking the injury to the effects of the birth of her first child in January, Radcliffe said: “Obviously it is a setback but I am trying to be sensible and do the best thing for the long term.” She added that she was looking to “Beijing and beyond” and reaffirmed that she hopes to continue at least until the 2012 London Olympics.

An earlier scan had shown a stress fracture to the right of Radcliffe’s sacrum, with a smaller one to the left, but the trouble has moved. “For some reason the right has healed and the left has got a lot worse,” she said. Radcliffe added that until this latest interruption, she had trained well and felt on schedule for Osaka, where she hoped to run in either the 10,000 metres or the marathon.

“I was not far off being able to race when it happened,” she said. Now relying on crutches to walk, she added: “It is a high-risk area coming back from pregnancy. The frustrating thing is that I was taking it gradually, doing a load of cross-training, which was probably stressing the sacrum.”

Asked whether the World Championships were in doubt for her, Radcliffe replied: “It is fair to say that I am not taking huge risks to ensure that I will 100 per cent be there, but I have not ruled it out either. Before this happened I had not got to the stage of going on the track but I think, from some of the training I have done, that I have come back stronger from the pregnancy.”

In 2002, Radcliffe won the London and Chicago marathons, breaking the world record, took gold on the track at the Commonwealth Games and European Championships and won the World Cross Country Championship. However, since then she has pulled out of one World Championships, one Commonwealth Games, one World Cross Country and one London Marathon through injury.

Radcliffe withdrew from the 2003 World Championships with a leg strain and missed the entire track season because of shin and lung troubles. She pulled out of the 2004 World Cross Country with a hamstring injury and failed to finish the marathon at the 2004 Athens Olympics.

Last year, a foot injury ruled her out of the Commonwealth Games and London Marathon. Her only “major” title since 2002 came in winning the 2005 World Championships marathon, although she has won the London and New York Marathons since then and World Half Marathon and European Cross Country titles. She has not raced seriously since December 2005.