When did the knee problem arise? Mine arose after I stopped riding. One doctor's theory was that cycling helped me create sufficient lubrication. I'm back to riding, and my knee pain is tolerable.

It has helped me a lot recently to have a bike mechanic install cleats on my shoes. He has an alignment tool to ensure that my feet point straight forward, because I have a tendency to point them out. The podiatrist told me to move my cleats back, and that has been a strange feeling, but it helps a lot. Another great help is to walk with my toes pointed forward, because I also tend to point them out when walking. I walk more consciously now. But recently, I find I can descend stairs much more easily, so these new things really help.

I have lots of bikes, and one of them has 155mm cranks, just as an experiment. Interestingly, they don't feel weird at all, so I recommend trying short cranks. They require the seat to be raised, but I don't mind.

For what it's worth, my pubic bone height is 32" or 33". My pants inseam is 30", which is to say I'm fairly short-legged. Still, I know a long legged cyclist who also likes very short cranks, so it's not crazy.