http://www.scuola-judo-tomita.com/gallerie_immagini/gallerie_kano_storiche/kano19.jpg

Jigoro Kano demonstrates a move that- while apparently illegal in modern judo- shows it's obvious potential for self defence (within the framework of more generalised skills, and of course after LOTS OF PRACTICE!).
I've not used this technique, not even practiced it in training (though I will give it a go, now!)- but any move that can secure an arm (which could hold a weapon), and then damage the elbow joint whilst simultaneously slamming the opponent's face into the floor HAS TO BE.........at least considered! Emoticono wink LOL

 Modern use in shiai
https://www.youtube.com/watch?v=wkGSPn_yoLA