I am not trying to “sell” you anything. I am just relating my own experience. You seem to think you know more about my own health history and my family medical history which has trends and my doctors’ advice, than I do. I can only relate again, that I am the only member of my family that was a runner throughout adulthood but all of my three brothers and a sister and my dad had knee replacement surgeries because of worn cartilage in their late 50’s and early 60’s. So I don’t really care what you “believe” you think you know about me.
There is a reason doctors asks for your family medical history when doing your history and physical exams. They are not just being nosy. The information is critical in understanding your own health condition. Cancers tend to run in families. Heart problems tend to run in families. Cholesterol problems tend to run in families. What you do to alter you lifestyle to avoid these issues has very little to do with the fact that you will tend to get the problem anyway because of your genes. Women with breast cancer, usually have other women in their family history that have had it as well. Men who die of heart attacks at a young age, usually are preceded by other male family members that have died young from the same event. And the list goes on.
Running marathons and other extremely debilitating forms of exercise increase the likelihood of cancer through the release of free radicals. Running as a form of exercise is extremely tough on the knee joint, even for someone who has no history or inherited condition.