I joined the Cane Club a few months ago when my knee got bad enough that making it to the bathroom in a timely manner got iffy...
After looking at the handles of the store-bought ones, I decided to make my own. I used a 7/8" hardware-store dowel, a crutch tip, and "furniture leg" from Lowes that's basically a flattened ball; about 2-1/2" diameter with the top and bottom cut off. I counterbored a hole in the ball, glued and screwed it to the dowel, and then kept cutting the dowel until it felt like it was about the right length.
What I found was that there's one length that's optimal for taking my full weight when my knee is completely uncooperative, and there's a longer length that's better for keeping my balance while walking. They're a bit over an inch apart. I split the difference and it works OK.
So far a number of people have been impressed by the big round handle; I've made a couple of canes as gifts to others who admired mine.
I don't know if the knee has simply had a turn for the better in the last few months, or if just taking some of the load off with the cane made that much difference. Like someone said way upthread, "It's not for the walking part, it's for the not-falling-down part."
Once you get to where you can't be absolutely sure a knee won't give way at the next step, you're forced into a gait that causes problems of its own...