well it is one of his really deadly moves.
wow should see the power of his knee kick esp that part where they
were near that petrol station,some guy in the car tried to take out
a guy,wow he flew over with a knew kick and that guy kena bang and
flew out the other direction.
Also muaythai emphasize alot on joints attack as it is a part of
the body that is really hard,so knee is one of them,the other being
the elbow.