In the medical term osteoarthritis, how many word roots are there?

First of all, it is very important to define the  "word root" in order to analyse the word "osteoarthritis" appropriately. So it might be said that a "word root" is the word part that is the core of a word and it contains the fundamental meaning of the word itself.
In the case of "osteoarthritis", it can be found the root "arthritis" which makes references to the inflammation of the joint and the root "osteo" which is associated with the the word bone. So the term would make reference to the inflammation of the bone joint.