heel hook is a leg lock affecting multiple joints, and is applied by transversely twisting the foot either medially or laterally. The torsional force puts severe torque on the ankle, which in turn transfers torque to the knee. The heel hook is generally considered to be a very dangerous leg lock, with a high rate of injury, especially to ligaments in the knee. It was subsequently banned in many combat sports featuring other leg locks such as Brazilian jiu-jitsu and Sambo. The heel hook is however an allowed technique in some submission wrestling and mixed martial arts competitions.