It does sound like more than a muscle pull, I think trying pred is worth a shot. I can't remember, did you try acupuncture? Is that a possibility where you are? When Sugar was almost 12, she started having spinal issues and almost couldn't walk (some days she could barly stand). A shot of pred got her temporary relief, and the acupuncture brought her back to about 90% mobility (with no more pred). Adequan shots also helped after she got going again.