Could also be the spaces between your dog's pads have filled with snow. It starts to spread the toes, it's cold, and it hurts.
If the snow is wet it packs into the spaces very easily and accumulates rapidly.
I can always tell when Lisl is ready to come in when she sits down or starts deciding which three legs she wants to walk on.
When we come in there are always snow or ice balls between her pads.
Bear, Anna, Molly, Ossie, and The Countess Lisl von Schlaf
An Unhappy German is a Sour Kraut!