I have an 8 year old barred rock hen, a fabulous layer back in the day, but with slowly worsening weakness of both legs over the last several months. She walks, but takes very small steps. She finds it very difficult to hop/fly to get up onto the 3 ft high compost bin, for example, something that was still easy for her last summer. It's obviously an effort for her to walk so she sits a lot.
Other than that, she is her normal self. Eats, drinks, and poops normally. Balance is normal. Alert and eager to go out when I let them out, but it's a great effort for her to do so. Just as excited as ever to get treats. Still maintaining her high status in the flock. I don't think she is in pain because she seems bright and of high spirits, but I know they sometimes hide it well.
I've examined her feet and legs and see nothing abnormal.
They get commercial feed - sometimes layer feed with added calcium, and sometimes higher protein "grower" that does not have a layer's dose of calcium, but always with oyster shell available right next to the feeder. As a treat every evening, they get a bit of scratch, sunflower seed, and dried mealworms. They usually have access to our compost which included kitchen scraps (thought they didn't have access to it over the winter).
Having had old hens, I think a bit of leg weakness with age is normal - they are never as springy as pullets. But this hen's degree of weakness is beyond anything I've seen in a hen this age or thereabouts.
What could be the cause? A spinal cord stroke? Arthritis? (though like I said, she does not appear to be in pain). Would appreciate any input. Thanks!