Glad you asked. My knees are actually fine. I do the right stuff like exercise, glucosamine, hot tub, etc. I wore neoprene sleeves the last ten years. My knees gave me trouble when I was around 50 or so. I had a mule that was injured. I had to walk her every day no matter what the weather. After a couple of months my knees were a lot better. Now I am 72 and walk a lot, even with a titanium rod in my femur and a bolt through my hip. The human body is an amazing thing.
My back is trouble. It has some arthritis. We played on concrete and asphalt some of the time. My bad injuries that I really feel are from skiing and horse wrecks.