Hello, I'm a new chicken mom and something similar happened with my only roo. I have a flock of 7 and they are just now 4 months old. My roo broke his hip just above his leg as you described and I immediately separated him from the flock. He was in pain right away and I set up a big dog kennel for him to stay in and try to possibly heal on his own so the girls wouldn't bully him bc he is injured as ive read chickens do with other sick chickens. I felt horrible for him. He's the sweetest thing. I gave him food and water and monitored him closely over the next 48 hours. He ate, drink and continued to use the bathroom so I felt there was hope. That was a month ago. He is now in a bigger kennel, standing up on one leg, hopping around, even putting weight on the leg where he broke his hip. He is also now roosting up high. I've had many people tell me chickens are so resilient, especially being young and will usually heal on their own with alot of love and TLC. I'm thinking another month of separation then I'll introduce him back to the girls. The main thing I was worried about was the pain he may he in but he never showed he was in any. Apparently chickens have a very high pain tolerance. I couldn't bring myself to cull him or give up on him. He stayed laying down for the first couple of weeks...then one day I came out to check on him and he was standing. Fix your baby a comfy place to heal and keep him separated. You will be surprised