Age usually means wisdom. At 63 my knees aren't what they used to be. I've learned to spin to keep the pressure off my joints.
This week I rode 315km from Kingston, Ontario to Montreal into a stiff 25km wind and my buddy and I used our heads. I transfered all the items from my bike onto his and then broke the wind for the whole trip so as he could draft. As soon as I felt pressure building up opn my knees I would drop a gear.
Probably the toughest ride of my life but at the same time it was very satisfying cuz my joints don't hurt at all.
Remember the story of the rabbit and the turtle.