The Hässelby runner, who won bronze in the Swedish Championships 800 metres last year, says she was out on a cycling session when she was hit by a car.
"After a sudden collision with a car, I flew about 20 metres. Then I was taken directly to hospital with several fractures and completely indescribable pain," Julia Nielsen tells the Swedish Athletics Federation's website.
On her Instagram account, she says she underwent seven hours of surgery for her injuries.
I'm glad I'm alive. Exactly what condition my body will be in later is still a bit unclear, but I'm hoping for the best.
Julia Nielsen, whose twin sister Wilma is also an elite middle-distance runner, also competed at Finnkampen last year. Her last race this season was the 1,500 metres at the Diamond League gala in Stockholm in June.
