I would say that 25% of all my sparring matches or drills involve a full-force knee collision. This is a pretty atrocious record, particularly since I’m supposed to be of the level where I can anticipate when someone is THINKING about kicking, and throw a killer double roundhouse/jumping back kick combo before their central nervous system even sends out a “Leg, kick!” signal. Oops.
One of these days, I will master the art of timing my kicks. Until then, I’m going to practice walking without bending my right knee.