Our puppy (a miniature australian shepherd) is 6 months old and I have a slight concern about the way his back legs move. At a normal walk they seem fine and move fluidly. Then, when he is between a walk and a run, they move almost in unison like a galloping horse, but in a very stiff way. Almost as if they are rocking back and forth or bouncing behind him. But at a full speed run he seems to move fluidly again. Is it normal for puppies to have this odd stiff sort of gallop? Or is this possible hip problems? Once cause may be that we live in an apartment with all linoleum floors. Any running he does in the house causes him to slide across the floor. We try to discourage running in the house and take him out for walks frequently. Could the linoleum floors be causing any problems? Thanks!