The Londonderry-born apprentice was riding Mount Rock in the attheraces.com Handicap for his boss Mick Easterby when the three-year-old gelding appeared to clip heels with the horse in front of him and was fatally injured.
Evans, who has had 38 winners this year, was taken to Harrogate District Hospital.
"He's fractured his pelvis and is still in Harrogate Hospital," said his agent Richard Hale.
"He'll be out of action for some time. Hopefully, he'll back early next year."
There was better news about Rachel Richardson, who was brought down in the same incident on Just Hiss. She also went to Harrogate Hospital but was later discharged.
"Rachel is OK. She's sound, she just has a few bruises," said the horse's trainer and Richardson's boss, Tim Easterby.
"I think she'll be riding out in the morning."