Bassett Hound can't use his back legs this morning - any experience with this?

11 year old Bassett just drags his back legs under/behind him. No falls or trauma known to have happened. He’s pretty lazy; I’ve only seen him run once when trying to get the piece of toast that my daughter had thrown to the floor. lol

Seriously, I am taking him to the vet, but I’d like to hear of your experiences with this while waiting for the appointment. Thanks!