
I know how you feel. My now 11-year old lurcher had had around 30 anaesthetics in his life-time so far. Started off with neutering, then stitches due to accidents and attacks from other dogs about 12 times. He has also broken a tooth that needed treatment under anasthaetics (twice), had TPLO surgery so was knocked out a few times for that (x-rays, MRI, surgery, x-rays again after), had a piece of twig burried in his skin that needed surgical removal, had his dew claws removed after injury, recently had x-rays after a leg injury, removal of fatty lump... He must hold some sort of record for the amount of anaesthetics he has had... LOL He is also hypothyroid. Yet, he is as fit as a fiddle and also has no problem with the vets and if given the chance wanders off towards the kennels every time we are there for anything... LOL
My saluki isn't so bad but has had a few mishaps in the last two or three years like a grass seed up his nose (needed knocking out to remove it), removal of his dewclaws after persistant nail bed infection, removal of lump, nearly sliced off his toe that needed careful stitching together of nerves and tendons and a damaged disc in his back which he had x-rays and MRI for...
Luckily my spaniels seem (so far) fairly robust with regards to injuries and accidents, though one is hypothyroid with associated allergies and the other may be hypothyroid too (testing at the moment). But overall these two are rarely at the vets - compared to the sighthounds. LOL
All I can say, please be persistent and keep at it with finding what is wrong. With both my lurcher and my saluki, the cruciate issue and the damaged disc issue were only discovered with an MRI... so perhaps that becomes an option for you if nothing else can find anything. A chiropractor is certainly another professional that I use if there are any movement issues as well, so another thing to look into.