As a fan of the TV series "Game of Thrones," I can only provide you with small satisfaction: Both in the TV series and the book it's stated that Jon Snow's direwolf "Ghost" doesn't have a specific height. But, based on people's common sense for Direwolves, which is scarcely ever wrong.
One could hardly miss this with all six feet of a Wormwood tree in their back yard. Or even worse, if a gardener were measuring his knee-to-heel distance with a ruler because he had no other way available! Remember, Ghost for all to see violated that mathematical probability by being not only smallest runt much swiftest and every bit of an athlete. Why can't he perhaps break free from natural height limits too?