What makes bunny back legs look knock knee

I have a 3 yr old Neitherland dwarf she has issues every winter. Gets skinny and back legs go kinda knock kneed. Each time it is medicine from the vet and critical care food. Then come spring she is her normal self. Last year she spent the winter in my dinning room and this year she is in the garage. I'm at a loss, she is never exposed the weather or wind. Had heat lamps which keep it above freezing unless it is really cold. Any help would be appreciated.

Ok guess no one has seen this she has another vet appt Friday. Thanks

What is her diet like? What country do you live in? Any other animals around?