Oh no.
I hope it's not.
Ask your vet to do and OFA patella exam. I will find the link with the instructions. An x-ray is a bad diagnostic tool for luxating patella. The x-ray will show the patella either in or out, and if it's in, that doesn't mean anything, and if it's out, the vet won't know the grade, so, manual manipulation is the best diagnostic tool. Don't waste the extra money on the x-ray.