Recently, from the library discard sale, I got a book published in the UK on Poultry Diseases. On Perosis it says:
--------------------------- Osteopetrosis (Thick Leg Disease; Osteodystrophia Fibrosa).The virus causing this condition appears to be related to that causing lymphoid leucosis. Itis characterized by increased osteoblastic activity in birds about 2 - 3 months old and is more common in the male than in the female. The long bones of the extreÂmities, especially the metatarsi, are thickened, deformed, and take on a boot-like appearance, which is characteristic of the disease (Fig. 5). The affected portions are hot and insensitive.
The disease is slowly progressive and ends fatally in about two months . It is transmitted from chicken to chicken and / or from turkey to chicken.
The lesions can be distinguished from those of rickets because the bone is deforÂmed without thickening, whilst in rickets the keel bone is often bent). In perosis there is also a twisting and flattening of the hock joint.
I gave up trying to upload the shot...Look over here.
https://flic.kr/p/BPomYa