The answer to that question may not be all of one or all of the other. Without calling up particular cases, it may well be that a panel would say that the service partially contributed to the osteoarthritis. The practical reality is that we all suffer from osteoarthritis—it's just a function of our being—and the question we have to ask is to what degree service contributed to the onset of that condition.
On May 31st, 2016. See this statement in context.