Our dog woke-up this morning limping, moving at a very slow pace if at all, having a difficult time standing and is very lethargic. it seems to be his rear right leg. I have lightly rubbed the entire leg, hip to paw inside and out, and his not flinching like i would think he would if it was painful to the touch. He is eating and alert and is not showing any other symptoms. He is a 2 1/2 year old pomeranion shih-tzu mix. He is not over weight, he's active, and just an overall happy dog. Any ideas?