Please please take your dog to a vet they may be something they can give the poor animal to help her, she obviously hasnt been to a vet for over a year, so how do you know what has taken her off her feet, it could be something quite simple like a vertabrae out of place which could be 'put' back in and then she would be on her feet again
I am sorry but by not taking her YOU are being very very cruel to her, she could have a very high pain barrier and not outwardly showing any signs of pain at all, as she is she has NO quality of life at all, she says she cries if you leave her that could be a sign of the pain she is feeling, you must get her to a vet asap, they dont just put an animal to sleep for no reason and if they can help get her back on her feet they will do, or even just some pain relief, but you really cannot put her through anymore without at least consulting a vet first.
I urge you to do this as a wheelchair may not even be suitable for her needs and actually make the problem worse.
Unless you take her to a vet I have no option but to close this thread as none of us are actually helping this dog with her suffering!!!!
Tashi - Forum Moderator