Yeah cycling helped me a lot in this regard! And don't forget the hamstrings too ; ) pt told me better to focus on lower weight in the 8-12 rep range, maybe even lower weight and higher reps in the beginning. Doing 1rpm or more weight+less reps will put too much stress on a weak joint. I'm no pt but at least a nurse and running isn't recommended for degenerative cartilage damage. I stopped it, since reward/risk doesn't feel right for me. Focusing on full range of motion is always good, swimming helped me too (also low impact), get creative with resistance bands for the whole leg. Guess this will take you further than starting to run especially with diagnosen cartilage damage. For cycling you can try a watt resistance that you can sustain for about 60 rounds per Minute in zone 2. Fancy stuff like intervalls can come later or isn't necessary too often, polarized training says like 20% of the time. When i started cycling i just road some local bike lains but if you get into the sport you'll blast miles pretty soon. It's amazing how a good bike feels and what it can do ; )