A leglock is a joint lock that is directed at joints of the leg such as the ankle, knee or hip joint. A leglock which is directed at joints in the foot is sometimes referred to as a foot lock and a lock at the hip as a hip lock. Leglocks are featured, with various levels of restrictions, in combat sports and martial arts such as Sambo, Brazilian Jiu-Jitsu, catch wrestling, mixed martial arts, Shootwrestling and submission wrestling, but are banned in some sports featuring joint locks such as judo.

As with other jointlocks, leglocks are more effective with full body leverage. Some attack the large joints of the knee or hip and involve utilizing leverage to counteract the larger muscle groups, while others directly attack ligaments in the knee or the smaller joint of the ankle. Leglocks can involve control positions such as the inside leg triangle or leg knot to maintain control while applying the attack or transitioning between two attacks, though they and some other control positions are banned in Brazilian Jiu-jitsu competition. Some other leglock control positions have been adopted into modern BJJ and submission grappling competitions as "guards" such as the snake guard, one-legged X-guard, and 50/50 Guard, where they are used for both leglocks and to reverse into dominant positions from the bottom.

A leg is a weight bearing and locomotive structure, usually having a columnar shape. During locomotion, legs function as "extensible struts" - the combination of movements at all joints can be modeled as a single, linear element capable of changing length and rotating about an omnidirectional "hip" joint.

As an anatomical animal structure it is used for locomotion. The distal end is often modified to distribute force (such as a foot). Most animals have an even number of legs.

As a component of furniture it is used for the economy of materials needed to provide the support for the useful surface, the table top or chair seat.

Many taxa are characterized by the number of legs:

In tetrapod anatomy, leg is used to refer to the entire limb. In human medicine its precise definition refers only to the segment between the knee and the ankle. This segment is also called the shank, and the front (anterior) of the segment is called the shin or pretibia.

In bipedal tetrapods, the two lower limbs are referred to as the "legs" and the two upper limbs as "arms" or "wings" as the case may be.

Frank Shamrock (born Frank Alisio Juarez, III; December 8, 1972) is a retired mixed martial arts fighter. Shamrock was the first to hold the UFC Middleweight Championship (later renamed the UFC Light Heavyweight Championship) and retired as the four-time defending undefeated champion. Shamrock was the #1 ranked pound for pound fighter in the world during his reign as the UFC Middleweight Champion. Shamrock has won numerous titles in other martial arts organizations, including the interim King of Pancrase title, the WEC Light Heavyweight Championship and the Strikeforce Middleweight Championship.

He was named "Fighter of the Decade" for the 1990s by the Wrestling Observer, "Best Full Contact Fighter" by Black Belt magazine (1998), and three time "Fighter of the Year" by Full Contact Fighter Magazine. He is a 7th degree black belt in submission fighting, awarded by O-Sensei Philip S. Porter of the United States Martial Arts Association. He is the adopted brother of former UFC champion Ken Shamrock. He holds notable wins over Bas Rutten, Tito Ortiz, Jeremy Horn, Tsuyoshi Kohsaka, Kevin Jackson and Phil Baroni. He is also the only man to defeat Cesar Gracie. He holds the Guinness World Records for Fastest UFC Title Fight Victory by Submission in 16 seconds over Kevin Jackson at UFC Japan in Yokohama Japan. An author, entrepreneur, philanthropist and social activist, he is a color commentator for Showtime Networks and a brand spokesman for Strikeforce.

Dean Richard Lister (February 13, 1976) is an American mixed martial artist and a former King of the Cage champion. He currently fights at the Middleweight division after moving down from the Light Heavyweight class. Lister's sparring partner and the former UFC light heavyweight champion Tito Ortiz invited Lister to be his assistant grappling coach on the third season of the Spike TV reality show, The Ultimate Fighter.

Lister grew up in a military family and lived in several South American countries, including Venezuela and Panama. Lister speaks several languages. He lived in Panama during the U.S. invasion in 1989, and, according to Lister, he was "right in the middle of a serious combat zone". After living in several different cities in the United States, Lister's family settled in San Diego for Lister's high school years.

Lister often fought as a kid, mostly due to a combination of being the "new kid", a foreigner, and being small for his age. The need to protect himself led Lister to wrestling and martial arts.

Erik Paulson (born 1966) is an American mixed martial artist raised in Minnesota and currently residing in California. He is the first American to win the World Light-Heavy Weight Shooto Title in Japan.

Starting with Judo in 1974, Paulson has trained in many disciplines including Freestyle and Greco-Roman Wrestling, Tae Kwon Do, Boxing, Jeet Kune Do, Filipino Kali/Eskrima, Sambo (martial art), Catch Wrestling, Shoot wrestling and Brazilian Jiu-Jitsu, studying first with Rorion Gracie, Royce Gracie, Rickson Gracie in his garage in 1989. He has studied with 40 different teachers over his 30 years of training including Rick Faye, Greg Nelson, Yorinaga Nakamura, Larry Hartsell, Tim Tackett, Ajarn Chai Sirisute, Nicolas Saignac, Rob Kaman, Rigan Machado, Rico Chipparelli, and the legendary Dan Inosanto, who claims Erik is one of the world's most dynamic grapplers.

He currently runs the CSW Training Center in Fullerton, California where he trains MMA fighters such as Josh Barnett, Ken Shamrock, Renato Sobral, Cub Swanson, Ben Jones, Craig Wilkerson, James Wilks and Ginelle Marquez. He is closely affiliated with Sean Sherk and Brock Lesnar of the Minnesota Martial Arts Academy.