How to Do a Kneebar in BJJ
The kneebar in Brazilian Jiu Jitsu is just like an armlock in many respects; it relies on hyper-extension to cause injury, you need to isolate the joint (which really means isolating the next joint up in the chain), and it's a straight joint lock submission. However, many gyms don't teach leglocks in general anywhere near as much as they teach armlocks, and as a result, there's an aura of mystery around the kneebar. This tutorial strives to get rid of this aura, while giving you a few different (relatively) easy ways to get into the kneebar, details on the finish, and what's really happening when a theoretical injury occurs.
A Simple Entry
This first entry is extremely generic, meaning you can hit it from a variety of different positions and situations, but you aren't likely to get into the technique in live rolling exactly as described here. Nevertheless, this type of entry is useful for a number of reasons, not the least of which is getting right into the submission itself so you can start practicing the details right away. Start by standing over your partner, facing them. Leaving your right leg in between their legs, step backward with your left leg, so that you can see their right leg through the space in between your legs. Make sure you're above your partner's knee with your hips (you can facilitate this by pushing their knee down with your hand while stepping backward). Now sit on your partner's hips, immobilizing them to an extent. For simplicity, let's call this the "gargoyle position" (imagine being a gargoyle on the edge of a roof, looking down). We'll talk about the finish details next (and look at another entry). For a deeper look at the toe hold finish, see How to Set Up a Toe Hold.
A Second Entry, and Finish Details
This second entry is surely one of my personal all-time favorites; I've had success in both competition and at the gym with this for a great many years now. Start from half guard bottom, blocking the crossface with your hands until you can get your head extremely close to your partner's right knee. Use your left hand to push your partner's left triceps up and away, and then use this space to swing your left leg over, in front of your partner, and then finish with your butt sitting on your partner's hips, up on your shoulder. Now push your partner backward (imagine twerking). As you come up on top, you're going to land in the gargoyle position, ready to finish.
The finish: Once you have landed in the gargoyle position, grab your partner's heel with both hands and hug it in close to your chest (make sure your chest is connected to their knee here). Using this tension, fall to the side, extending their leg completely. Make sure your neck is glued to the top of their foot or their ankle! Now, squeeze your knees together tightly, and bite down with your heels, allowing you to use your hip strength to hyper-extend their meniscus (and for some other bad things to possibly happen).
Follow Up Sweep
Once your partner has gotten used to the above sweep, you'll want to add this one in. As you go to sweep your partner backward, you notice that they are driving into you. Just use this momentum to throw them forward, kicking with one leg to build momentum for the other leg. The finish is the same here. Additional entry detail: sometimes you can grab your foot in order to get your leg across to the other side of your partner's hip; this is ideal whenever they post on the ground, stopping the initial leg swing motion. I like this technique a lot because it relies on your partner's knowledge base (they've got to stop the initial push-back sweep from earlier), and you can utilize pendulum-style momentum when executing the sweep.
Kneebar or sweep?
Half the Game
Leglocks are half of the joint-lock game; after all, there are two elbows and two ankles on most humans with two legs. Why not become good at attacking them? It is important to note that most sport BJJ competitions prohibit kneebars for white through purple belt, but allow it for brown and black belt. However, many (if not most) no-gi competitions allow kneebars. The moral of the story; know the rules well if you're planning to compete, and have at least a basic understanding of all allowed submissions. As always, let me know if these techniques work for you (and make sense!).