by Thomas Kurz, co-author of Basic Instincts of Self-Defense and author of Stretching Scientifically, Secrets of Stretching, and Science of Sports Training.
With practice, this combination may become so devastating as to completely stop an attack.
Now the technique: The attacker faces you. With your foot jab the attacker's nearest knee. If the attacker leads with the right leg you will do the foot jab with your right foot. Hit the front of the attacker's knee with the ball of your foot. It does not have to be a snappy, crisp kick. A quick, strong push to the knee will do. Just put your foot quickly on the attacker's knee (so he or she does not evade) and push to lock the knee. With this push you may even manage to dislocate it.
As soon as your foot jab makes an impression, put that foot down on the ground and with your other leg kick the attacker's thigh. Depending on the distance and position, you can kick with your shin or with your knee. Kick the outside surface of the attacker's thigh approximately one hand width above the knee. This is where the nerves cutaneous femoris lateralis and femoralis (rami cutanei anteriores) run. Another way to learn the location of this spot is to stand upright and extend your arm along the side of your thigh. The spot will be at the tip of your middle finger.
Do not retract your leg after the impactfollow through. This kick will paralyze the attacker's leg and spin the attacker away from you. A powerful kick to that spot makes one feel like throwing up.
To develop power in the shin kick, practice on a heavy bag suspended low or on a shield held by a partner beside his or her leading leg. The shield must be thick enough to protect your partner. Kick for maximum impact and follow through with enough power to spin or turn your partner.