In reply to Dominion: Thanks for telling me about your dad's experience.Glad to hear he's still v. mobile without knee replacements.From what I've researched myself,seems cartilage replacement research has moved on lots,but the surgery and rehab are complex.Results are fair for femoral cartilage defects in young athletes - results deteriorate significantly if you're over 35-45;i.e not much hope for most of us yet.I'm wondering if he wore out or tore his menisci - the c shaped fibrocartilage cushions between femur and tibia.My prob. is a hyaline cartilage defect under patella -prob caused by an abnormal lateral tracking of the patella, tho' I believe the foot on the affected side does pronate a bit under heavy load (20-30kg rucsacs).The knee is amazingly complex.I asked on the forum just to see how many of us fellrunners were running on- or not, with cartilage probs.I'm trying not to fill the website with clinical knee stuff-because I could easily do that single-handedly - and I don't consider that I know that much! Your dad hasn't missed out on any relevant new technology though! Thanks again!