Many times when breaking down the grappling of a fighter phrases like "he has great hips" or "good hip mobility" will be used, but rarely is it fully explained to readers what this means. When trying to control a fighter, the top man must control the bottom man's hips and put them flat on the mat. To keep from being pinned flat, bottom fighters will execute the hip escape, one of the most basic techniques in grappling, also sometimes called "shrimping".
Here is the basics of the technique:
Shrimping/Hip Escape Brazilian Jiu-Jitsu - www.learnbjjtechniques.com (via Jon Foster)
Notice that the student doing the demonstration is turning to be on his side before using his leg to push his hips away. It is impossible to do a hip escape while flat on your back, so that turn, however slight, is crucial to moving the hips. The posted foot and the shoulder that is on the ground carries the weight of the student, making the hips light and makes moving them easy. It is a full body movement and as the hips move back the student curls his back, finishing in a position that looks like a shrimp, creating maximum movement of the hips.
Hip escapes are used to create distance between fighters and can be used to escape a bad position or help get to a position to create leverage, execute a submission or just get back to standing. This movement is so vital is included in the warm ups of basically every grappling school to help commit it to muscle memory.
The act of turning onto the hips or moving the hips is a key aspect of working from the bottom and some form of the hip escape is present in just about all bottom work in grappling. Now the this basic version of the hip escape is great for warming up but sometimes it isn't enough in live sparring. Top position grapplers could already be controlling the hips or putting down so much pressure that hip escaping can be difficult.
To solve this problem many chain the hip escape with a bridge, that relives pressure for a key second for the bottom fighter to scoot his hips away. Here is Pedro Sauer black belt Keith Owen explaining that very concept:
The Art of Shrimping in BJJ by Keith Owen (via Submissions101)
As mentioned above, hip movement is crucial part of bottom work in grappling and this is true in MMA. It is rarely form perfect, but a hip escape is often a prelude to escaping back to the feet or getting into the proper position to sweep. As grapplers progress they often become so competent at moving and rotating their hips they don't need to execute a proper hip escape, but the basic concept remains the same: don't be flat on the ground and create space to move the hips.
The hip escape is a key competent to some of the basic position escapes in Brazilian Jiu Jitsu. Here is Jeff Monson demonstrating a basic escape from side control back to guard, notice the hip escape he does around 2:57.
Jeff Monson Side Control Escape (via grapplevideos)
When mounted many fighters seem to rely on trying to explode and buck the fighter on top of them off, but when this doesn't work they are often stuck. One prime example of this was Fedor Emelianenko's loss to Antonio Silva, who mounted Fedor several times. Fedor attempted his explosive bucking escape but Silva's base was just too strong. Another possible escape is executing hip escapes, trying to get the hips out from under the mounted fighter. Known as the knee-to-elbow escape, it is a very basic and very effective move.
It is, however, risky because attempting to do it because it leaves openings for strikes. So timing is key with the knee-to-elbow and it is often paired with a buck, as Keith Owen demonstrated above. Here is UFC founder, Rorion Gracie teaching the knee-to-elbow escape:
So that is the hip escape and some of its more basic applications in grappling. If you are vigilant you will some variety of it any MMA fight that hits the ground and is a sign of at least some basic ability when it comes to grappling.
The sport of MMA is constantly changing and not being trapped under strong top position grapplers is become more the norm as the realities of judging limit the paths to victory for a bottom fighter. Hip mobility is key to staying active from the bottom or escaping to the feet, and I'll leave you with former UFC Heavyweight Champion Frank Mir speaking at a seminar about how he has changed his own bottom game to help create more mobility.
Frank Mir (part 3): Half Guard for MMA and moving your body in unison (via Submissions101)