Some might say Derby the dog is disabled, but clearly they haven't seen him in action.

"He has always been the happiest dog I know," Derby's adopted human, Sherry Portanova, tells The Dodo. But before he met Sherry, things weren't so bright for him.

Derby was born with underdeveloped front limbs, and although he was otherwise a healthy dog, that one difference nearly caused him to be put down. The young dog's original owners decided they didn't want him anymore, and he soon wound up at the Peace and Paws Dog Rescue shelter in Hillsborough, N.H. But he wasn't unwanted for long.

Fortunately, Derby soon met someone who was not only compassionate enough to save his life, but also equipped with the know-how to improve it too.

(YouTube/3D Systems)

That person was Tara Anderson, director at 3D Systems, a company that specializes in 3-D printing. When she heard about Derby's condition, she knew she had to do her part to give him a second chance — and perhaps find a solution to his mobility limitations.

After taking Derby in as a foster, Anderson set him up with a wheeled cart to make it easier for him to get around. And while it certainly did help, Anderson suspected that her team of designers could do one better.

(YouTube/3D Systems)

The skilled staff at 3D Systems soon set about crafting a custom set of prosthetic legs that would not only help Derby to move more naturally, but that would also let him live out his full potential as an energetic pet. Several design attempts later, they finally settled on an oval-tread shape, designed to fit Derby's unique anatomy.

(YouTube/3D Systems)

But even before getting that special gift made just for him, Derby found something even more important — a forever home with a new family who loves him, differences and all.

To Derby's adopted parents, the Portanovas, he was just an all-around happy dog, though he was soon about to get a whole lot happier.

(YouTube/3D Systems)

The day came recently for Derby to try on the prosthetic limbs, and for the very first time in his life, experience the joy of running.

"It was incredible and emotional the first time we saw him run on his new legs," Sherry says. "Incredible because it was his very first time on them and emotional because he was so excited to be running."

(YouTube/3D Systems)

Since then, Derby has barely slowed down, using his newfound freedom of movement to join his family on real runs around the block and to experience life a bit more like dogs who weren't born different like him.

"Derby was born with this deformity so he never really knew any different; he was a happy dog," says Sherry. "However, his new legs have allowed him to run on concrete, play with other dogs and overall be more mobile."

Check out footage of Derby in action below: