Those big-boned dogs are sometimes prone to "growing pains." Had she been running before this? Oh, and I know you love her and everything, but be careful about giving her tooooo much attention for limping ...

My parents' dog one twitched when Dad was cutting her toenails, no he nipped the quick by accident. Well, he and Ma felt bad, so were very sypathetic while she "recovered." Well, now, years and years later, if I'm visiting Dad and not paying enough attention to Bruni, she'll limp into the room. The first time this happened, I asked Dad what was wrong with her paw. He smiled, bemused, and said "Nothing. Keep watching." Well, when she resumed walking the limp had changed sides ... she forgot which foot was "hurt!"