Duckling with an extra leg joint? Help please!

[Feanor]

I just got an order of ducklings in. Two of them splashed in their water and got soaked (in their initial box lined with paper towels) so I took them out to dry under a heat lamp on dry bedding. Then I noticed that one's foot looked lame, and on inspection it looks like it has 2 knee joints? Like her thigh bone has a bulbous knee on it above its real knee. I thought maybe it was broken and tried to stretch it out to see if I could splint it and I cant. Could this be a birth defect or a partially heeled break?


You can see its natural "knee" pointing to the right and further up is another joint in the thigh bone before it connects to the body

 

[ChickenRaiser95]

I had a chick hatch with the same leg problem. I don't know what to do about it. It is just 2 days old. It can kind of walk-scoot and eat, but would rather sleep and not do anything. She is very weak. The leg on top in the first picture is the one with the extra joint.