From 2016 Laws definitions:
Kick: A kick is made by hitting the ball with any part of the leg or foot, except the heel,
from the toe to the knee but not including the knee; a kick must move the ball a visible
distance out of the hand, or along the ground.
From Law 12 definitions:
A knock-on occurs when a player loses possession of the ball and it goes forward,
or when a player hits the ball forward with the hand or arm, or when the ball hits
the hand or arm and goes forward, and the ball touches the ground or another
player before the original player can catch it.
Note the parts in red.
So a kick is only foot to shin and a knock-on is only off the hand or arms.
In dispute are too separate scenarios:
A ball lost forward that is then struck by a player with his foot before it strikes the ground. Is that a kick? I would allow it but others here would not.
A ball deliberately bounced off the knee is, by definition, not a kick. But what is it? It isn't a knock-on but would you allow it? Where is it covered by law?
Sorry, Lewis, more questions than answers.