LOL, why do you think there is anything wrong with ones knees at 60? Mine at 63 are as good as at 23. No one in their 40's, 50's, 60's etc is as athletic as in their 20's, but it's not like arthritis starts setting in when you hit 60. In fact, I climbed a 14er in CO a couple years ago, no problem. 60 sounds old until you get there. If one halfway takes care of oneself, you'll be surprised how it isn't. Perhaps you meant a 90 y/o. ?