How long have you noticed the swelling? Can you see any swelling in her hock joints? Would it be possible to get another picture of her standing that shows her feet, toes, and ankles? It can be hard to tell articular gout from bacterial or viral arthritis sometimes.
What do you feed your chickens? Gout can have many causes including heredity, feeding high protein diets, too much sodium, dehydration, mold exposure, and others. Some have said that using sour cherry concentrate has had a positive effect on gout. Here is a good article to read:
https://thepoultrysite.com/articles/gout-management-in-poultry