Yeah, a lot of sports have specific injuries, some are pretty bad like in NFL football. Many of the contact sports have ACL and all sorts of joint injuries.
Even golf has injuries as the repetition is hard on the joints and back.
If people are cycling on a flat road and have a cadence of over 60, I'd say that is very safe. Just don't crash if your a senior citizen...lol (I'll be there) If a cyclist does hills, I'd say the knees will eventually take most of the stress and have a higher probability of injury.
Knees get effected even at a higher cadence? I thought hills can be done by spinning, without hurting oneself
When the hills get steeper, most cyclists will 'stand' on the pedals and the force on the knees is greater. This over years/decades will eventually wear down the knee.