Ormerod had been hailed as one of Great Britain's strongest medal bets in the build-up to the Games after securing a series of World Cup podiums in both slopestyle and Big Air disciplines.
Grainger, who clinched rowing gold at London 2012 and is now chair of UK Sport, said: "Only in time will it sink in what she has missed out on here - she's much younger than me and has already had more injuries than I had in my entire career.
"If you handle these things right it can make you a better athlete - it becomes part of your character and you can be better for it.
"I know she will get past this and come back more enthused in four years' time. She has always come back stronger from these setbacks and I'm sure she will again."
In Ormerod's absence, Aimee Fuller will be the only British competitor when qualifying for the women's snowboard slopestyle competition takes place on Sunday.
Ormerod's cousin Jamie Nicholls is due to be one of the first Britons in action at the Games when he enters men's snowboard slopestyle qualifying with compatriot Billy Morgan in Pyeongchang on Saturday.
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