Perhaps the best way a fundamentals student should look at the Knee on Belly (KoB) position is as an attack position.  While you can maintain the position for a short period of time, you don’t need long to determine if you have a valid attack or you should be transitioning.  In competition, you need to hold the position for 3 seconds, and this alters the style used.  The lowered stable position you often see in competition has 3 seconds of maintenance for points as it’s goal before moving on to mount, unless the opponent does something grievously wrong.  Rather than treat knee on belly as a points position, we are going to look at it as an attack position, which is a better place to start from than simply looking at ways to maintain it for a matter of seconds. 

Control

Knee on belly tends to be a position that you transition to quickly.  It can be obtained from side control, or after a passing of the guard.  For simplicity, we’ll take a look at getting knee on belly after side control.

To start, get good grips at the back of the collar and on the pants.  If you can’t get the pants grip, place your hand on the floor, or as a last resort, get a bunch of the jacket material and belt.  Once you have grips, slide your knee that is near the hips up and over your opponent’s belly until your foot is against their near side.  Your other knee should come off the ground, with 90% of your weight on your opponent’s belly.  Neither foot should have any significant weight bearing on it.

There are a number of variations of knee on belly.  Some are more uncomfortable for you opponent, opening them up to mistakes, and some require a bit more finesse to maintain but give you more attack options.  This version will keep you out of the most trouble, and give you plenty of options to work with.

Make sure your foot is against your opponent’s hip.  If there is space between your foot and their hip, it gives them more escape options.  Your shin should be immobilizing their hips, and you should be pulling up on the pants and the collar, like you are bending their body up against your shin.  Keep an upright posture, driving your weight into your opponent’s belly.

In this position, you should be able to absorb and substantially counter different bridging directions as well as restrict rotation and rolling.

Defense

This is perhaps the shortest amount of instruction for defending a position.  Keep your elbows in.

You need to keep your elbows near your body, and don’t let them get out to the side.  Any gap between your elbows and body will be exploited.  Also, your hands should be ready to protect your neck.  Any time your hands drift away from your neck, it’s in danger.  So if you have an escape in mind, go ahead and execute it, but if something goes wrong, or you aren’t getting it right away, just make sure you have a clear path back to protecting your neck.

For example, this means that if you must push something away, like stripping a grip or pushing an arm, your motions should be short and without letting your elbows get away from your body.  After you have done what you need to do, then immediately get your hands back into a defensive position.

One note about the video.  I’m a proponent of crossing my arms at the wrist as a default defensive posture.  In the video, I inexplicably have my arms crossed the wrong way.  The reason that is the case is because my outside arm is in more danger of attack than the inside arm, which means I should have my inside arm over the outside arm to discourage a simple attack.

Summary

Knee on Belly is far more than just a temporary position for scoring points.  It can be a highly dynamic position that allows a wide variety of attacks.  It is also a good position to reinforce some choking attacks since it helps to immobilize the hips, making an escape even harder.  From a defensive viewpoint, your arms and your neck are in constant danger, and you must be disciplined about keeping your elbows in tight and your hands always at the ready to defend your neck.  The pressure on your stomach will be very uncomfortable, but you are just going to have to deal with it and resolve not to end up in that position in the future.