also: ひざかっくん
knee dislocation; knee giving way
Refers to the physical condition where the knee joint becomes dislocated or suddenly buckles. Often used in medical or injury contexts.
I suffered a knee dislocation during the rugby match.
making someone's knees buckle; knee-buckling prank
A prank or action where one person hits the back of another's knees with their own knees, causing the victim's legs to suddenly bend. Colloquial and often used among children or in playful contexts.
My friend did a knee-buckling prank on me from behind, and it startled me.