Yes, that is right, just what snakemama said. They are graded 1 to 5, with 5 being the worst. Grade 5 requires surgery, I think grade 4 surgery is optional. Riley has a loose kneecap which may pop out now and again, but pops back into place on it's own. She would feel pain while it is out of place, once it pops back, the pain ends, though there may be some inflammation. In the 48 hours she has been here I have not noticed it as an issue. So for now we won't do anything for it.