Is running bad for your knees?
NO!
Studies have shown that runners actually have lower rates of knee osteoarthritis than sedentary people.
The impact that running provides helps to stimulate bone building which is why if you are at peri/menopause age/having cancer treatment which may reduce bone density or if you have osteopenia, then you should include running/jumping and stomping movements in your training plans.
Knee injuries which occur during running are often caused by doing too much too soon. These overuse injuries happen when we put the body through a cumulative stress which it is simply not strong enough to handle.
Knee injuries are frequently caused by injuries further up the chain, so, before you blame running for your knee pain, look at including exercises to strengthen the glutes/hips and core (as well as not being too eager and building your running up too quickly!)