To win a fight you need to be more effective then your enemy. Being more efficient means using better weapons.
The three most effective weapons out of the human body are; the knee strike, the elbow strike, and the headbutt.
While the elbow strike is the easiest and fastest of them to learn, the knee strike is the most powerful of them all. A good knee strike could end the fight on the spot. Defiantly worth the practice time.
The key to a powerful knee strike is speed, proper use of body weight, and accuracy. All possible to obtain of course through practice.
There are three major possibilities to deliver a good knee strike;
Straight knee- (also called the front knee) this involves thrusting the knee into the groin, sternum, or head of the opponent, while standing in front of him. A good knee strike into anyone of those main targets could end a fight, or give the option for an easy follow up with more strikes.
Side knee- this knee strike dose not use the forward thrusting motion like the straight knee. Instead, it's rotated from the outside. This strike is used when extremely close to the opponent and there's no distance to use the straight knee. The target for this strike should be the floating ribs. Very easy to break.
Flying knee- this strike is very similar to the straight knee strike, expect it's preformed by jumping, giving the strike a lot of momentum. Generally, this strike should be used more in the ring then in the street. However, it's a great strike to use as a follow up to end the fight, because of the amazing knock out power it has. For example; striking the opponent with an effective elbow strike, following up with a straight knee, and for the grand slam a flying knee. Really ruin his day.
Many people know this theoretically, but don't practice it enough. Knee strikes should be drilled again and again. Make it your second nature.
Another aspect of course to train and to become very familiar with, would be closing the distance, allowing you to use your primary weapons; the elbow, knee, and head.
ICCS head Instructor