Getting behind the kneecaps 

Having sex / most likely doggy style

friend 1: man i brought this girl over last night it got crazy “
friend 2: Were you “Getting behind the kneecaps” crazy?

friend 1: hell yea

Getting behind the kneecaps by Papa_stem82 April 28, 2021

Niko Niko Kneecaps 

The following definition occurs if Carl was a weeaboo, and Paul needed therapy from the trauma. (Llamas With Hats)

"Niko Niko Ni!"
"I WILL BREAK YOUR NIKO NIKO KNEECAPS, CARL!"

Niko Niko Kneecaps by -trash- February 13, 2022

Bust Your Kneecaps

To fuck standing up so long your knees give way underneath you, as though they've been busted.

And then Becca told me that she was gonna' bust your kneecaps for your birthday.

Bust Your Kneecaps by Dating A Canadian 101 March 29, 2014

Ashy kneecaps

When a female is giving a male head and scoots on her knees to keep up with the male while he backs around the furniture, making her knees ashy.

Claire: Me and my man did the ashy kneecaps last night.

Candy: girl ain't no lotion gonna fix that over night.

Ashy kneecaps by DALGS13 June 9, 2013

say goodbye to your kneecaps chuckle head

boink
bonk
bap
kneecaps mine now

person 1: say goodbye to your kneecaps chuckle head
person 2: ok *rips off kneecaps*

say goodbye to your kneecaps chuckle head by the scout that takes kneecaps September 19, 2022

Nico Nico Kneecaps 

A phrase used out of annoyance when someone says "Nico Nico Nii" one too many times.

Person 1: Nico Nico Nii!
Person 2: Nico Nico Nii!
Person 1: Nico Nico-
Person 3: Dude. If you don't stop, I'm gonna break your Nico Nico Kneecaps.

Nico Nico Kneecaps by LiterallyBored March 26, 2022

Your mother's kneecaps 

A fuckin funnier way of saying your mother's poes

Trist:"storman your a dickhead "
Storman norman: your mother's kneecaps
Tristan:" nest your a fuckboy "
nest "your mother's kneecaps bitch

Your mother's kneecaps by Your mother's kneecaps August 20, 2016