How old is she? Can she move her toes or lift her leg? Are her toes curled under? In the picture, it looks a bit like she may have a slipped hock tendon, which can occur with leg bone deformities, and in grown hens with an injury. Mareks disease could also be a possibility, but I would first rule out a vitamin deficiency, injury, or slipped hock tendon. Mareks usually affects unvaccinated young chickens between 3 and 25 weeks old, although it can strike any age. It can cause lameness or paralysis in one or both legs or wings, wry neck, lack of immunity to common diseases, tumors, skin irruptions, and sometimes eye changes. Get a good poultry vitamin containing riboflavin (B2) at your feed store, or use 1/2 tablet of BComplex crushed into feed daily with a little vegetable oil added. Make sure that she can reach her food and water, and if she is worse confine her to a basket or crate near it.