Starting in Brazilian Jiu-Jitsu after having done Judo, I forget when I first became familiar with leg locks. I knew a rudimentary ankle lock moreso for a turnover than a submission, but that was about it.
I had occasionally seen them in MMA and submission grappling tournaments, but knew little if anything about them. As I got ready for my 3rd MMA fight, one of my coaches went over some basics of the heel hook as it was the most dangerous of the leg attacks legal in MMA in my home state where I would be fighting. As it is, the figure four toe hold/"Comprido" is my favorite foot/leg attack in terms of having submitted with it in training.
I did some research and found that foot locks and leg attacks in general have long been viewed as cheap, a move of the suburbs, less qualitative than other submissions in the Brazilian Jiu-Jitsu arsenal.
I'm a big fan of "what works" and that if "it works" then it's not all that cheap, lame, gay, or whatever else one might say to decry it.
A bit of history on the footlock and leg attacks from wikipedia and Oswaldo Fadda:
"Despite being regarded by the Gracie family as an outcast, Fadda managed to open his own academy on the outskirts of Rio on January 27, 1950. He and his students began specialising in the use of footlocks, an often ignored part of the jiu-jitsu curriculum. The next year, Fadda felt confident that his school was ready for the next step and issued a challenge to the Gracies through the media: "We wish to challenge the Gracies, we respect them like the formidable adversaries they are but we do not fear them. We have 20 pupils ready for the dispute... Fadda's team emerged victorious, making good use of their knowledge of footlocks, in which the opposition was lacking."
Since I've decided to devote a week/7 days worth of posts to attacking below the belt, the time has come to discuss Masakazu Imanari, the "10th Dan of leg locks" as he is known.
He has something like 9 submission victories via toe hold or heel hook in MMA and highlights of his grappling tournaments make clear he wins with them in non-MMA matchs as well. He also has wins by RNC and armbar as well.
Masakazu on wikipedia
Masakazu's fight record on sherdog
The Definitive Masakazu Imanari Interview via The Grappling Dummy (a great website and online store in it's own right):