Nambroth thank you so much for your help. We have had 2 hens die within the last year. The most recent one, a month ago, was egg bound. We are unsure of the cause of death of the other one. It died about 6 months ago. Four days before she started limping, we added a new rooster to the flock. I have since contacted the previous owner to see if he has experienced this with any chicken in his flock. He said he had not. I am truly at a loss because other than being unable to walk, she is completely herself. Alert, healthy appetite, vocal and still laying.
I have read through the information you posted and with all them, the paralysis seems to be accompanied by other symptoms. I had read an article about giving them baby aspirin for injuries causing paralysis. Do you have any knowledge of this treatment? I greatly appreciate all of your help!
Baby aspirin is safe, as is Metacam-- Metacam is something you would either need to order online or get it from a vet (cat and dog vets have it, they might sell you some if you explain your situation even if they won't see the chicken!). I will look up the dosage for you! These are mostly therapeutic in that they are a pain management and offer some anti-inflammatory relief, so they aren't a cure, but might help if she is hurting!
The egg binding in your most recent death (so sorry to hear it!) may have been a stand-alone problem (it often is, sadly) or a complication from something else. If the hen was older, or of a breed that lays more heavily, it could have easily just been its own problem.
Did the other bird that died 6 months ago show any symptoms at all?
I want to be very honest, I am not an expert, and while I have studied Marek's disease a lot, I am only starting to dive into research on other diseases (free time is at a minimum in my household) so I just want to be clear, I am much less educated on some things than others! I know with Marek's disease, which can indeed show up as only leg problems in some birds, it has an incubation period of 3 weeks. Meaning from time to exposure, it takes at least three weeks for symptoms to show up if a bird is going to show them (some birds don't show them for months or even years!). So, four days is not enough time for your hen to develop symptoms of Marek's disease from your new rooster, at least! This does not rule Marek's out entirely, as it could have been in your flock for longer and your other birds are showing now signs, or it could have come in on the environment. But this is hardly a diagnosis either!
Still, let's look at other problems first, since there is not much that can be done if it's Marek's.
Is there any chance at all that there is lead that your girl could have gotten into? My vet advised that she's seen birds develop neurological problems (often leg paralysis) from ingesting as little as a single BB (which chickens often mistake for a lovely piece of grit) or even birds eating old paint flakes. Lots of things used to be manufactured out of lead, and if you live on a property that is a bit older, there is a chance.
What are you feeding, exactly? Is there any chance at all that it may have gotten moldy?
Is she still eating well?
I sincerely do hope that she recovers, but if she passes, you might want to consider sending her for testing. It would give you a lot of answers and it makes it much easier to deal with your flock in the future if you know what's going on. Back when I lived in TX, Texas A&M used to do necropsies for a low cost; I don't know if they still do but I know they do diagnostic blood testing.