My dog's gait has suddenly changed and now her back legs shake/shiver occasionally

My 5-year-old Cavapoo has suddenly started to walk a little funny, and I just noticed that her back legs seem to shiver/shake slightly whenever she's standing or lying down. She doesn't have any prior health complications, and she's about as healthy as a dog can be at her age.

I first began to notice her issue when we had to stay inside for a little over a week without a good, long walk. (Snowstorm) I thought that maybe she just needed exercise, so after the snow cleared up enough, I took her on a bunch of long walks, about the same as I would usually do, but the problem persisted.

I did take her to the vet, and they said something about her having malformed kneecaps, and that sometimes they pop out of their sockets or get loose or whatever, but they said it was nothing to be worried about.

It's been a week since that visit, and she still walks differently than she did before the snowstorm. It's as though she's putting less weight on it, but it can't be causing her much pain because she still runs and walks without showing any signs of discomfort. It's probably worth noting that she is a bit more tentative to jump up onto chairs and such.

The main thing I'm concerned about is the leg tremors/shivers. Does this mean something is wrong? What can I do to help her if it does? Here's a quick video that shows her leg shaking when she's lying down.