We had a hen like this the other week. Found in the house sitting, couldn't walk without using wings to balance and even then had to lie down after not long. Brought her in and cleaned up her feet to check but nothing on them to indicate injury. Non weight bearing on the right leg and it was trembling like crazy (just the bad leg not the rest of her), but both legs were the same in terms of temperature. Leg wasn't swinging oddly and nothing felt broken. She was also able to grab onto my fingers with the toes on the bad leg. She was eating and drinking fine so long as it was close. Vet said it could be Mareks but keep an eye on her and see if she goes downhill.
Kept her confined in a small dog cage, cleaning her out daily. She seemed quite subdued and I could place her on an old feed bag when I cleaned her out and she just wouldn't move. Tried her after 4 days in the conservatory and she hopped about and didn't need to use her wings. Kept her in the cage for another 3 days after that. Might have kept her in longer but the snow had thawed, I could see the other hens sunbathing in the garden and she had started pecking me when I cleaned her out and showing signs of being frustrated inside. So we popped her out and checked on her regularly. She stayed near the house (with feed and water) but hopped quite happily and wasn't seen lying down once. She got herself to bed, although didn't jump up to the perches.
By the next day she was late for corn but she ran (Still limping) like a bat of hell after my hubby with the corn. Within a week she was back up on the perches. She is still limping a bit but I'm feeling pretty confident it was a sprain or something. Hope your hen makes a good recovery. I had a bit about it on my blog with a video of how she was at the 4 day release, but not much other new information.
Dans