Derby is a canine whose front legs are underdeveloped at birth. Running was nearly hard for him, and he frequently suffered injuries from face-to-ground contact.
His mobility was increased by a standard wheelchair, but his interactions with other canines and his speed were constrained. The no-kill shelter that spared Derby from being put to death and a set of modern 3D printed prosthetic legs gave him the best opportunity to have a normal life and run for the first time in his life.
He is still getting used to his new legs, which will eventually be replaced with bigger ones.
With his humans, Derby now runs 2 to 3 miles every day, and as you can see in the video, he appears to be really content with his new legs.