I would soak the foot and scrub it clean, then look again.
Maybe a tiny string is wrapped around the joint, or maybe it is bumble foot.
Bumble foot will have a scab somewhere. There has to be some spot where the foot was wounded and infection entered.
The scab once soaked might gently peal off, hopefully still connected to any nasty infection kernal that might be there. Then flush the wound. Supposedly you are then supposed to use antibiotic and pack and dress the wound.
The two times I had bumble, I just cleaned them out and popped the chicken back down in the same dirty chicken coop. Both times (different chickens each time), it didn't come back.
Thanks! I tried to give you an ovation....but my iPad is not cooperating. I'll try later

1kluckychik, we have Russian olive bushes all over our property. (Very invasive), anyway, being me.....I tried one of the "olives" once I found out what it was
