I have an 8-yr-old border collie and springer spaniel mix (my vet thinks). Lucy has always been like a puppy despite her age and loves to jump and go for walks and dances ecstatically when very happy, like when going for walks. Her favorite activity is running so she has a run at least once a day and usually more.
Last week I had to leave her for a week at some friends to take care of my sister's animals (Lucy and one of their female dogs hate each other). The friends love her, and she them, and she got good care. I picked her up Thursday night and took her for a walk that night, twice on Friday, and twice on Saturday, and she was normal in every way.
Suddenly, on Sunday, she could not jump into the truck as usual to go for a walk. I had to lift her up. But she walked completely normally. Same today. She cannot get up the steps to come into the trailer where we live, but there is no limping or favoring of her legs at all, no evidence of pain. Her appetite is as usual. She does not have the puppy enthusiasm as normal and doesn't run as she loves to do, but seems otherwise healthy and happy. In any other dog her age, she would appear totally normal, but she isn't normal for her. She simply can't jump into the truck, get up the steps, and is barely able to jump on to the bed. She will go for walks, but she doesn't get crazily ecstatic when I mention a walk, the way she normally does.
She CAN jump out of the truck or go DOWN the steps, although she hesitated a little today.
Everything else I've read discusses loss of function in the legs that can be obviously seen, like dragging a leg, limping, shakiness, pain, etc., but no obvious problems with those. She doesn't seem tender when I feel her legs.
I have a Veterinarian's appointment for her tomorrow, but I'm wondering what ideas you might have now, as I'm quite worried.
Lucy is an epileptic but does not have frequent seizures...about once every four to six months.
I have not seen her have a bowel movement in the last few days, although she may have had. She usually has one on our walks.
A few weeks ago, I had to put out mouse poison (D-Con) because the mice were taking over and avoiding all traps (about three different types). She cannot get to this poison and has had no interest in mice, dead or alive. I dispose of them when I find them. I don't think she has eaten any mice.
She has had no ticks.
She has lipedemia on her chest that is growing quite large but does not seem to bother her.
The friends she stayed with for a week were unable to take her for daily walks because of their age and health, but they had a big yard for her to run around in and played ball with her.