That space under your knee; the scientific name is not known. Generally this area does not grow coarse hair unless you accidentially rub rogaine on it. If such a thing was done, you'd have a hairy knee-pit.
Girl 1-"Ohmygod, I was shaving my legs last night and cut my knee-pit! Now everytime I squat down more blood gushes out D:"
Girl 2-"Yoh at least your older brother didnt wipe rogaine all over it when you were sleeping, my brother did and now I have a hairy knee pit!"
The pit of your knee... (behind the knee cap... where it bends... yeah)
My knee pit's name is edward!
(noun) The southern cousin of the armpit which lacks both elongated hair and a vile musk; this pit requires little to no maintenance.
My knee pit is chafing me.
He would often bring his knee up to his chest and fold his leg in while vivaciously fingering his knee pit.
The back of the knee
Ass! You hit me in the kneepit.
The back of your knee of course!
My kneepits are all sweaty!
Underneath the knee
Your arm has an armpit, your knee has a kneepit. Also known as the kpit.