translated for u

grade 1
The kneecap can luxate: With a stretched leg its possible to move the kneecap by hand. and when moved back to normal mode it automatically shoots the kneecap back in the right position
grade 2
With this grade the pattella regularly shoots of and stays luxated for a longer or shorter time
By regularly on and off shoot of the patella caused osteoarthritis and cartilage flattening of the slot.

!!

from grade 3 it stays off, when u put it back it shoots back out