There's really no evidence that running is hard on your joints, as long as you avoid serious injuries. If anything, studies have shown that those who run regularly have better mobility in old age.
I have seen that research too, and I believe it. However running is bad on joints for many people, including me.
I believe the difference that makes the difference is how good your joint alignment is before starting. If your alignment is bad the running can chronically damage the joints, if your alignment is good they will get only slightly damaged and regrow stronger, leading to the results shown in the studies. Survivorship bias means only people with good joint alignment will actually run enough to be included in a study.
