It started with a rolled ankle during a routine training exercise.
Shannon Hubbard never imagined it was the prologue to one of the most debilitating pain conditions known to exist, called complex regional pain syndrome.
It's a condition that causes the nervous system to go haywire, creating pain disproportionate to the actual injury. It can also affect how the body regulates temperature and blood flow.
For Hubbard, it manifested several years ago following surgery on her foot. That's a common way for it to take hold.
"My leg feels like it's on fire pretty much all the time. It spreads to different parts of your body," the 47-year-old Army veteran says.
Hubbard props up her leg, careful not to graze it against the kitchen table in her home east of Phoenix. It's red and swollen, still scarred from an ulcer that landed her in the hospital a few months ago.
"That started as a little blister and four days later it was like the size of a baseball," she says. "They had to cut it open and then it got infected and because I have blood flow issues, it doesn't heal."
She knows that soon it will happen again.
"Over the past three years, I've been prescribed over sixty different medications and combinations, none have even touched the pain," she says.
She holds up a plastic bag filled with discarded pill bottles — evidence of her elusive search for a solution to the pain.