I would suspect mycoplasma synovitis. How do the hock joints look? I have not seen articular gout, but in pictures, the whole foot and toes appear lumpy. If you do a necropsy there will be white urates deposited on the joints and on organs, which is a result of kidney disease.
MS may be treated with Tylan, tetracycline drugs, and others. I would recommend a vet.
MS can be diagnosed with a PCR test that may be done by a vet or poultry lab. Here is a lab I saw online:
https://zoologix.com/avian/Datasheets/Mycoplasma.htm
Here is a good article on MS in poultry:
https://www.merckvetmanual.com/poultry/mycoplasmosis/mycoplasma-synoviae-infection-in-poultry
In this link there is a good picture of articular gout:
http://www.thepoultrysite.com/articles/3509/gout-management-in-poultry/