Have 3 different hens, all roughly 7 years old. We inherited them from a friend who's is having medical issues and can't take care of them. They had about 20 acres that they had the run of and lived. They've always had somewhat knarly looking feet, have had them 9 months with no real issues until about 2 weeks ago. I'm guessing bumble foot but wanting a better answer than my guess, never have found they little black spot or anything on their feet to show a puncture, they don't limp or seem to have any issues getting around.
Haven't had mite or any other issues in a year and just getting over a week of sub zero weather and another foot of snow.... worried though with the way the scales are lifting.
That is really bad Scaly Leg mites. They are microscopic, so you won't see them but they cause the scales to lift like that and the feet and shanks to look gnarled. Treatment is to smother them in oil or grease. Some people use Vaseline, others dip them in paraffin or smear them in coconut oil. I've used Vick's Vapour Rub with some success as well as Protection Plus wound ointment for horses which contains Citronella in a thick greasy pink gunk. You need to reapply regularly whatever you use. Every other day at least and best if you can soak them first in a warm Epsom Salts bath and give them a gentle scrub with a soft brush before drying and applying the ointment/grease/oil. Good luck sorting them out and well done for giving these old girls a new home.