"Damaging your knees" is often associated with degenerative joint disease or gonarthrosis. Interestingly, running as a hobby can lower the risk of developing osteoarthritis. While research on the effects of running on professional athletes has yielded mixed results, a 2017 meta-analysis found that non-professional runners have a lower chance of developing osteoarthritis than sedentary individuals or professional runners.
Running itself is not primarily responsible for osteoarthritis, but rather other factors such as being overweight, age, heredity, poor posture, insufficient exercise, improper form, incorrect training/rest schedules, wearing poorly fitting shoes, running on hard surfaces, and an unbalanced diet are more likely to contribute to its occurrence.