Had exactly same thing happened to me her back legs were paralysed, IF i remember was about a week before she could stand unaided and a couple of weeks before could get up one step, she was also have a bugger of a time havin a pee or the like. Then she took about a month to get back to norm. But that was well early in the year so i gave her 6 months rest.
Bit of a bugger this time of the year