I hear ya. Two years ago I did the S.Kaibab/Bright Angel trail. Back was okay, but the knees! I didn't expect steps in the Grand Canyon (who was the fool who thought that up?).

On the way down I stumbled over a piece of rebar sticking too far out of one of the logs, went down on the soft part of the knee. Wobbly the rest of the way down.
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Life should not be a journey to the grave with the intent of arriving safely in a well preserved body, but to skid in broadside, thoroughly used up, worn out, and loudly proclaiming Wow! What a Ride!