In the film, which is based on a true story, the Winter's Bone star portrays a polio-stricken author named Mark O'Brien, who hires a sex therapist to help him lose his virginity.
But Hawkes admits he may have gone a bit too far in dedicating himself to the role - and he is seeking the aid of a chiropractor as he attempts to reverse the damage he caused to his back.
He tells New York Magazine, "Mark’s spine was horribly curved. When you read the script, it says, 'I haven’t seen my penis since I was six years old.' And Helen Hunt, as his therapist, says into a tape recorder: 'His spine is so horribly curved that I don’t know if intercourse is possible.' You need to honour those things.
"I invented, along with the lovely props people, something called the torture ball, which was a soccer-sized piece of foam that I would lay onto the left side of my back in order to curve my spine.
"It turned out to not be very good for me and my chiropractor told me that my organs were migrating. I probably will carry some of that the rest of my life, but it’s obviously a minute amount of pain compared to what many disabled people face minute-to-minute.
"I don’t know what it’s called, but my spine now has not enough movement... I’ve been doing yoga for like 25 years, but my spine doesn’t have enough movement in one direction and the opposite direction has way too much movement. (My chiropractor) doesn’t know how to fix it other than I might wear a brace for a while."