Knee
noun
The kanji and the word are exactly the same.
Since this word is made up of a single kanji, it probably uses the kun'yomi reading. You've learned them already, so you should be able to read this on your own!
ピザを膝の上で食べるのが好きです。
I like eating pizza off my knees.
レンタル彼氏に膝をついてプロポーズしてもらうには追加料金が10万円もかかる。
Having a rental boyfriend propose on one knee costs an additional 100,000 yen.
私の母は膝で歩くレースの世界記録保持者だ。
My mom is the knee-walking race world record holder.