When dogs experience an acute change in behavior, its likely because they are in pain, or something is wrong with them. Pets can't come up to us and say, "Hey, my hips been bothering me, do you mind taking me to the vet to see what the problem is?" so they have to get our attention in other ways. Going potty in the house (or out of the litter box, for cats), nipping when you pet them on certain areas of their body, etc.

You say she has hip displaysia and artiritis, this could very well be the culprit. She could be in a "bad" or "grouchy" mood 'cause she isn't feeling well!!