Looks like a leg deformity to me.
https://www.merckvetmanual.com/poultry/disorders-of-the-skeletal-system-in-poultry/noninfectious-skeletal-disorders-in-poultry-broilers#:~:text=Valgus%20or%20varus%20deviation%20of,in%20turkeys%20than%20in%20chickens.