"Knees up, Mother Brown!" If only I could..

I think my knees, especially the left one, are finally giving up on me. They hurt and the keep going snap, crackle and pop like some demented breakfast cereal. I am going to the doc next Wednesday, and will inform a waiting world of the outcome.
Note "especially the left one", and I think I know why it is so. Decades ago, I was in the Highlands with a colleague, who persuaded me to tackle a Munro. We finally got to the top, he with ease and I with a great deal of panting. I placed the obligatory rock on the obligatory cairn.
Then I asked my colleague what was the technique for going DOWN a mountain. He said "make like a goat" or words to the effect, ie, zoom down in a series of short, rapid jumps. So I did make like a goat, and for the next six months, my left knee was strapped up and I had to walk with a stick. And now, I suspect, my sins have come back to haunt me. If I ever meet that colleague again, I will make like a goat and butt him in the trossachs.