It could be pano. Normally a puppy problem but I have seen it as old as 5 year old. I would also check for lymes disease. Is he in a kennel? If so, what are you cleaning the kennel with. If he is in a kennel he may be jumping upright too much and causing stress to his hind legs. Also, even tho he is ofa certified is there a chance he tore his ACL? There is something else that a friend dealt with but I can't remember what it was called, sounds exactly what you are describing. The toenails would not be an issue unless they tore off. He might also have sensitive pads wich is not good if you plan on getting any titles such as the AD on him. Look at his feet/pads, if they are reddish it is an enviromental issue, even if he is a house dog carpet cleaners, floor cleaners, laundry detergents etc could be an irritating factor. just some food for thought
Denise
i agree make sure theres nuthing stuck in his feet his nails are trimmed and he has the correct size kennel-he should be able to stand turn around and lay down on his side without his feet being cramped, it sounds like hes allergic to his food make sure there are no corm or any by-products in there, if that doesnt help take him to the vet..good luck
Have you taken him to the Vet? If his nails need trimming then that could be the problem.
Does he have something stuck in his feet? I would take him to the Vet and get it checked out.