Three years ago, Theresa Hannigan, 61, lost the ability to walk due to an autoimmune disease that has slowly been settling throughout her body since she was 27 years old. Now, thanks to an innovative robotic exoskeleton, the veteran has regained mobility and gotten her life back, she says.

Hannigan was first asked to be a part of research into the ReWalk Personal System as a patient at James J. Peters VA Medical Center in the Bronx, N.Y., but she didn’t have enough upper body strength to qualify. She went home and trained until about a month later, when she returned and asked to be reconsidered. By this time, she was about 10 months into having to use a wheelchair.

“I kind of begged them, tugged at their hearts to give me a shot,” she said. “They gave me the opportunity, and here I am four years later using it, so it paid off.”

The ReWalk exoskeleton was invented by  Israeli inventor Dr. Amit Goffer, who became quadriplegic after an ATV accident in 1997. The personal walking system is Class II medical device— the first and only of its kind to receive approval from the Food and Drug Administration (FDA). The weight of the device stands on its own, meaning that users stand on their bones, which improves their health, Larry Jasinksi, ReWalk CEO, told FoxNews.com. Users stand inside the device on foot plates and motors, and gears on the side of each leg are sized for each individual. A pelvic band holds it together around the waist.

What makes the ReWalk unique, Jasinski noted, are unique components: a tilt sensor and the natural gait it creates. The tilt sensor senses when the user leans forward, triggering it to allow the individual to walk. When walking, each foot strikes the ground heel first, then toe. This efficient movement mimics the natural human gait, and its efficiency allows its backpack battery pack to last all day.

“It’s a learned thing to walk again, but once they got it down, the biggest problem I have is sometimes when I show people the equipment, I can’t find them because they’ve walked away,” Jasinski told FoxNews.com.

Dr. Alberto Esquenazi, chairman of the department of physical medicine and rehabilitation at MossRehab in Philadelphia, consulted ReWalk during early development of the device, helping the company refine the walking pattern by providing insight into the proper physical ratio and timing of movement that occurs at the hip and knee.

“When you walk, your hip bends at about half of the range that your knee bends— people don’t realize that. Your hip works a lot less than your knee from the perspective of movement … because they’re carrying the whole load of the hip muscles, they have to work harder,” he told FoxNews.com.

Understanding that balance helped developers better generate simulated walking using an algorithm that adjusts for each patient.

“ReWalk was intended from the beginning for individuals with complete paralysis with spinal cord injuries. It was expanded to patients with incomplete injury, meaning they may have some movement but are profoundly weak, and patients with other disease presented in a similar manner, such as MS,” Esquenazi said.

ReWalk users must use crutches for balance, and to tell them where their bodies are in space and where their legs are in relation to the rest of their bodies.

“Individuals who have spinal cord injuries not only lose motor control but also the ability to move their joints … they have no idea where their legs are in relation to space,” Esquenazi said.

Hannigan’s recovery

Hannigan, who served as a medic on air evacuations during the Vietnam War and was medically retired in 1976, had always been athletic. Her disease left her family concerned not only about her medical health but also about her mental health. Unable to even get herself out of bed and dressed, she became depressed.

“I went from staring at the walls and wondering what my future was going to hold … [ReWalk] saved my life. It really did,” she said.

Hannigan was medically approved for the ReWalk, and the first time she put it on and stood up, she cried tears of joy. By the end of three days of hour-long training sessions, she was able to walk while someone held the brace to steady her. In a month, or 12 hours, of training, she walked without assistance.

“I was doing something the doctor told me I would never be able to do,” Hanningan said.

As one of 54 patients who has a ReWalk for home use— 84 of the devices are used in rehabilitation centers— Hannigan had to teach herself how to use the device for everyday life, like learn how to get a bottle of ketchup from the fridge to the kitchen table and make her bed.

“It never ceases to amaze me each day that I strap it on, there’s always something new for me to learn, a new challenge that it presents each day because, like anything else, we push the limits,” she said.

The FDA’s program requires that Hannigan is always accompanied when using the ReWalk, which she found somewhat hindering at first, but working with her partner, Pat, has helped her learn how to use the ReWalk for daily tasks. Once they figured out how she could ReWalk with a grocery cart, Pat now stands guard, rather than actively helping her.

Two years ago, Hannigan went to Israel to meet ReWalk’s inventor and was the second person Goffer saw using the device. It happened that President Obama was also in the country and was introduced to the device with a demonstration by Hannigan.

“He asked how it benefitted me, and as soon as I gave him an example, he got it,” Hannigan said. “He asked if the device could help his father-in-law, who has multiple sclerosis … and asked [the inventors, ‘What do you need?’”

Hannigan has been able to become active again, and for the past four years he has participated in The National Veterans Winter Sports Clinic in Aspen, Colo., downhill skiing, playing ice hockey, even learning how to scuba dive in a heated pool.

“It helps you mentally, you know, gets stuff squared away, keeps you active,” she said.

“Ask anybody walking in a ReWalk— it’s been a life-changer for every single solitary one of us,” she said. “It’s not just mental. The physical well-being has changed also.”