The 34 year old, from Santa Fe, New Mexico, is one of just 25 people in the world born with bilateral PFFD (Proximal femoral focal deficiency) type D. This means his knee bones fall beneath his hip bones.
Despite the condition, he is able to walk - the only one in the world to do so.
Speaking to Barcroft TV, Hrdlicka says that despite the pain brought on by walking, his girlfriend Chelsee Stewart - whom he met on Facebook - makes his life infinitely better.
Chelsee and I are about a foot or so in difference in height.
The height difference between us never really affected me. I’m used to having people be way taller than I am.
Picture: Barcroft TV screengrab
Chelsee supports me, emotionally in a way that I’ve never had in my life before. Whether it’s just to put a smile on my face or a glass of cold water. She is there.
Stewart recalls the first time she met him, she was wary of the height difference.
Doctors had informed him that if he had been born with thighs, he would have been over six feet tall.
When they met, he stood at 4 foot 6.
When we first met, I did think the height difference was going to be sort of a problem because this was my first time really being with someone that much shorter than me. It took us a lot of time to really learn what works and what doesn’t work but now it’s just like normal.
He is very capable of doing a lot of things, more than I would have ever expected, really.
Having this condition sometimes can really get to him, especially with the pain that he goes through. But me being able to support him and make him smile when he is in that pain and really show him that he is loved, changes his perspective during those times.
Another challenge for Hrdlicka is full-time employment. Given the nature of his condition, day-to-day tasks like walking prove to be difficult for him.
To be able to cover expenses is very unpredictable. That’s been my biggest challenge and trying to keep a stable job where you can be reliable every day. That’s why I guess, I lean towards doing things like jewellery because then I can go on my schedule.
You can see his story in the clip below:
You can donate to Nathan Hrdlicka's GoFundMe page, which aims to raise money for him, here.