[scientizscht (OP)]

Hello

Can you tell me please what is the pathogenesis of osteoarthritis?

What exactly goes wrong and where the problem lies?

I know the joint is inflamed, there  is loss of joint tissue, etc, but what is the exact problem that causes the disease?

[evan_au]

Major causes are mechanical stress, coupled with an inflammatory response.
You could start here: https://en.wikipedia.org/wiki/Osteoarthritis#Risk_factors

[diverjohn]

I have osteoarthritis of my hip joint. Because I am not overweight the joint probably lost its smooth surface from hard activity. I used to play volleyball, and later I ran 9 marathons. Am currently 64 years old. None of my parents had osteoarthritis.