What breed of dog and how old????? Sounds like disk disease or a herniated disk of the spine.....You can google IVDD (Intervertabral Disk Disease) and read up on it........Karla
It's a young(1 and a bit) years old pitbull.
I now the pain and cost of rescue adoption, so I ask is there any evidence of physical abuse, do you have any history on the dog? Some rescue dogs are just given over to rescue because the owner can not afford (time/money) to keep them. Other dogs are rescued from an abusive/neglect and sometimes physical damage.
I ask that given what you have provided. A young strong dog like a pitbull should be very resilient.
Hope misfits4me jumps back in, I am reading more out of sympathy than knowledge.
Well, there is a chance he was abused, but at least in XRAY no damage was shown.