The contacting point on the knee is a test of courage for the flyer. The center of gravity must be (as always) above the contact point, which is just below the knee. This requires a straight hip. It’s not easy to land on your feet when you tilt forward… but the flyer should trust his base, or delete that position from his repertoire.
This figure is often called Knee-Marie because of its humble position.
A simpler version of this position is the high Z, in which the flyer is additionally supported with the hands on the shoulder of the base. Again, the hip is above the contact point on the knee! The lower leg, thigh and upper body of the flyer produce the shape of a crooked Z. This position is also used as an entrance for the Japanese, in which the flyer ends in the handstand on the shoulder of the base.