Steve, 4 1/2, started limping a week ago.  Initially, I thought it was due to the frapping while on his daily walk but he was walking normally afterward (he always fraps at the same place during his walk).  The limping started about 3-4 hours after his walk.  I confined him to one room to avoid stairs and any more frapping.  The next day, he's walking fine one minute and then starts limping.  By the third day, he was limping in the morning and when I came home for lunch he didn't want to put any weight on the rear right leg.  By the time I had to go back to work he was doing a slight limp.

Went to the vet and doctor manipulted his leg to check for torn/injured ACL.  The doctor didn't think it was his ACL but wanted to take x-rays as he did have a limping episode on the same leg before.  Good news is his ACL is OK and his hips look good.  Problem is they found Steve has a extra lumbar vertebrae.  WHAT?  an extra vertebrae?  So this extra vertebrae could be causing a pinched nerve and causing him to limp or not put weight on his rear right leg.

Going to the vet again tomorrow to get more info and next course of treatment or if we need to go see a specialist.  Steve is on Rimadyl now which is helping but I'm really worried about him. 

I'm trying to read up on anything related to what the doc said but any experiences, pointers, ideas, tips that you could share would be very much appreciated!!!!