It's just a pulled muscle. For a big dog, he's getting up in years - but, not being there or seeing him, I think it's too soon to be thinking that.
When it's time, he'll let you know.
One of the hardest things I've ever done was taking Riley on his final ride. But, he finally looked at me that morning and his eyes said "this isn't fun anymore".
I cried like a little girl that day.
A few weeks ago I put $2000 on a surgery for Dyce, my 12-13 yr Border Collie. I only spent $50 when I bought her...
She's doing great!
Don't give up on Buddy.