Rylie has low grade luxating patella and has had it since she was 2 or 3 years old. It's never been bad enough for surgery. Right now she's on Glycoflex III, and has been on it for maybe 2 years? She's 8.5 years old. Anyway, she's been acting strange lately. I have a vet appointment for her tomorrow morning, but I wanted to see if anyone had any thoughts on what could be going on. We're going to run a full blood panel as well. This started a few weeks ago. She will have mornings where she doesn't want to come down for breakfast. She'll hide under the bed and shake. It looks (to me) as if she is in pain. Her legs will shake and she'll hold her ears back. At first I was assuming her knees were bothering her, but after reading about arthritis in dogs it seems it could be that as well. If I do happen to get her to come and eat, once we get outside she's ready to bolt back in the door. Normally she's the dog that never wants to come back inside... so it's just odd behavior for her. It has happened maybe 1-2 times a week. She's back to normal within a couple of hours... acting playful and like her normal self.