The only problem with hanging around with lots of people with lots of dogs is that you hear the worst stories as well as the best. One of the shelties in our club was a regular in the USDAA top-10 16"-agility list. Owner came home one day and found him pretty much paralyzed. Apparently suffered a stroke in the spine. Is walking now, but stiffly. Agility days are gone.
Another friend works at a vet clinic. She said someone came in on Wednesday with a dog he thought was dying and didn't know why. Came home and found him sprawled and struggling in the yard under a tree. Broke his spine. Best guess is he was jumping up after squirrels and came down wrong. Had to be put to sleep.
I watch Jake's legs, knowing he's got arthritis in the lower spine. He seems to sort of stumble over his back legs or lose his equilibrium briefly there, but always corrects within a step or two and keeps going. Last night in agility class, while we were practicing aggressive Snooker moves, he turned into SuperJake, which I haven't entirely seen in quite a while on the agility field. Then once in a while I hear him drag his back toenails as he walks, but then he stops doing it as soon as I pay attention.
Amber had such arthritis as she got older, with the dragging back feet and sometimes she couldn't stand up to go to the bathroom. And Sheba of course had horrid times standing the last couple of months, dragging those back toenails again all the time, although it's not clear whether it was arthritis or something else going on in her spine. But she was about 17 (and we knew it because she lived with us for all but the first 6 months or so), so that's not unexpected. But that was why we finally had to put her to sleep--couldn't stand up on her own. Nothing wrong with her mind or her will to keep going.
Things That You Can Do Nothing About But That Can Hurt You In The Middle Of The Night Just Thinking About Them.