A family friend of ours has well over 50 ducks- so I talked to him about it. The leg is obviously broken, how it was broken is a mystery- it could have been born that way or it could have been hurt while trying to get away from a predator, got it stuck, etc. Most wild animals like ducks will adapt to the disablity and live out their lives like a normal animal of their kind. There are some vet offices and wildlife rehabilitators that could try to fix/repair the leg. My dad and I found an injured Mallard hen with a broken wing and leg, our local animal shelter is also a major wildlife rehabilitator- we took her their, they fixed her up, and set her free.