while now (~2 weeks) one of our older hens (Georgette) has been having trouble bending one of her legs, and it's causing her a lot of trouble moving. We first thought that she'd simply sprained her leg, and it should heal after a while, but recently a second, much younger, hen (Houdini/Hendini) has developed that problem as well, so now we aren't so sure.
Summary: Two adult hens can't bend one of their legs easily, had it for 2 weeks and 1 day respectively, not sure if it's coincidence or some disease.
I'm sorry about your hensWell, I now think it's likely just a coincidence that these problems happened at the same time, Hendini just hurt her leg somehow, but Georgette is plain and simply dying. She's been a pretty good hen in the time we've had her, but we think we might need to put her down.

Can you post some photos of both hen's legs and feet?
Is there any swelling of the joints?
Have you added any new chickens within the last 30days?
You're going into Spring(?), have both been laying eggs through winter or have they just come back into lay?
Since you have 2 with similar symptoms, it could be disease like Marek's, but I would still look at environment too. Think back, has anything changed - type or brand of feed/treats, did feed get moldy, access to compost, any pesticides/oil/weed killer, etc.?
You mention that Georgette is dying, so sorry about that. Have you felt her abdomen for any bloat, swelling or fluid? Crop empty in the morning? No lice/mites?
I know it's more questions than anything, but just trying to narrow things down and rule out some possibilities. Sadly, sometimes we just don't know what's going on until one passes and the body is sent in for necropsy. Since there's 2 of them, getting some testing done would be a good idea.