Based on shoe size.
The knee sleeve was recommended to me by a friend who is involved in long distance walking.
So I researched the Incrediwear website and ordered a pair. I am walking every day as i am doing the Camino in Spain this summer.
Since wearing the knee sleeve, the pain and discomfort in both of my knees has reduced if not disappeared altogether.
I am extremely happy and satisfied with the knee sleeve and would recommend any of the products produced by Incrediwear.