I do not think it is right choice for her. First we have to make sure that she is not having problems due to nerve
compression. I would suggest you to get EMG/NCV test of her both leg.If there is nerve compression then TKR will not be helpfull. Thouh if she had normal nerve test then you can plan TKR for her. You can forward her reports on this forum . I will try my best to help you.