My knees have always given me a problem. Eventually it turn to be not only OA but gravel under the knee cap. The left knee had orthoscopic surgery twice. Better for a while. Then cortisone injections. That graduated to HA injections. It is like Karo syrup being injected under the knee cap. Very painful, but great results. 20+ years and I have not had the replacements they told me that I needed. My legs are crooked. Both the legs have a bend to the left causing the rubbing. Think bow legged one way.
So check X rays to see what is going on. The rubbing will make your knees swell.
Thanks ! I’ve had osteoporosis for years due to another condition so need to way my odds carefully.