Dogs that are in pain act just like humans do: They behave differently from normal. Dogs may withdraw, become listless or overly affectionate. They may bark, whine or act unusually aggressive. Often, dogs in pain lick, bite or protect a certain part of their body. Their appetite changes or they soil in the house. Dogs with arthritis may walk stiffly or have trouble getting to their feet. Look for these and other signs of unusual behavior.