ひざかっくん 膝カックン
"Knee joint attack." A physical [[prank]] where one individual deliberately bumps into the back of another's knees using their own, often causing them to lose their balance and fall. A group may also willingly do this to each other for the thrill of the chain reaction. 

h4.See also
* "Wikipedia article":http://ja.wikipedia.org/wiki/膝カックン
* "A simple depiction":https://45mix.net/wp-content/uploads/gazou/hiza_kakkun-Opt.gif (animated GIF)
* [[kanchou]]
hiza kakkun