Yeah, I was thinking it might be hereditary, too, since he's a pure bred Araucana. He was bred to be rumpless & I wonder if this is one of the results of trying to breed for that trait. When I first inspected him after this started, there was no swelling or seemingly broken bones, but his hip joints did pop a little. Like they were catching on a tendon when he would try to bend at the hip.
I'm 99% sure he's a boy. He's 9 months old. Never laid an egg. He has pointy hackle & saddle feathers and when I have crowing contests with the other roosters he joins in. When he first started walking like a penguin I inspected him for a bound egg just in case, and there was no egg-like mass. His belly is soft. Plus, if he was egg bound I think he would've died by now. I thought of that, too. It seems to be a common reason for this behavior. But no, he's a boy.
I do let him out of the cage daily, but he can barely walk at all now. He mostly just falls. It seems to have gotten worse over time. I'll post a vid.
The penguin walk developed literally overnight about a month ago.
Here's another pic.
I just really want to make him better because now that I've brought him inside to nurse him back to health, well, now I love him and he's a pet. But the hubby won't agree to any more vet bills for birds that don't produce eggs.