LESSON NOTES · レッスンノート

N4Lesson notes · Oct 4, 2026

Knee in Japanese: 膝ひざ (ひざ), 膝枕ひざまくら, 膝ひざを打うつ, and 膝ひざを交まじえて話はなす

"Knee" in Japanese is 膝ひざ (ひざ), usually written in hiragana as ひざ. "My knee hurts" is ひざが痛いたい, resting your head on someone's lap is 膝枕ひざまくら (ひざまくら), and to kneel is ひざまずく. The idiom 膝ひざを打うつ, "slap your knee", means a sudden "aha!" moment.

In Japanese, ひざ covers both the knee and the lap, so sitting on someone's ひざ means sitting on their lap. This small overlap explains a lot of cozy anime scenes.

How do you say "knee" in Japanese?

What does 膝ひざ mean?

膝ひざ (ひざ) is the knee. It also means the lap when you sit.

ひざが痛いたくて階段かいだんがつらい。 — My knee hurts, so stairs are hard. (casual) 猫ねこがひざの上うえで寝ねている。 — The cat is sleeping on my lap. (casual)

Why is it usually written ひざ?

The kanji 膝ひざ is hard to write, so hiragana is common in daily writing. You will see the kanji at clinics and in books.

If you need to describe knee trouble at a clinic, the simple phrase ひざが痛いたいです works well, and you can add 曲まげると (when I bend it) or 歩あるくと (when I walk) to explain when it hurts. That gives the doctor useful detail, and it uses grammar you already know.

What is 膝小僧ひざこぞう?

膝小僧ひざこぞう (ひざこぞう), "knee boy", is a cute word for the kneecap area, often used about children's scraped knees.

転ころんで膝小僧ひざこぞうをすりむいた。 — I fell and scraped my knee. (casual)

What is 膝枕ひざまくら?

膝枕ひざまくら (ひざまくら), "lap pillow", is resting your head on someone's lap. It is a classic romantic or caring scene in anime.

疲つかれて、母ははの膝枕ひざまくらで寝ねてしまった。 — I was tired and fell asleep with my head in my mother's lap. (casual)

What is ひざまずく?

ひざまずく is to kneel down, for example in a proposal or before a king.

彼かれはひざまずいてプロポーズした。 — He got down on one knee and proposed. (casual)

For marriage words, see married in Japanese.

Word Reading Meaning
膝ひざ ひざ knee, lap
膝小僧ひざこぞう ひざこぞう kneecap
膝枕ひざまくら ひざまくら lap pillow
ひざまずく ひざまずく to kneel
膝ひざを打うつ ひざをうつ to have an "aha" moment
膝ひざを交まじえる ひざをまじえる to talk closely
膝ひざが笑わらう ひざがわらう knees go weak
膝掛ひざかけけ ひざかけ lap blanket

What idioms use 膝ひざ?

What does 膝ひざを打うつ mean?

膝ひざを打うつ, "slap your knee", is the moment you suddenly understand or agree. なるほどと膝ひざを打うった is a common written phrase.

その説明せつめいに思おもわず膝ひざを打うった。 — That explanation made me go "aha!" (written style)

For a related word, see I see in Japanese.

What does 膝ひざを交まじえて話はなす mean?

膝ひざを交まじえて話はなす, "talk with knees together", means to have a close, open conversation face to face.

一度いちど、膝ひざを交まじえて話はなそう。 — Let's sit down and talk properly. (casual)

What does 膝ひざが笑わらう mean?

膝ひざが笑わらう, "knees laugh", is when your knees shake and go weak after a long hike or hard exercise.

山やまを下くだりたら膝ひざが笑わらっていた。 — After coming down the mountain, my knees were shaking. (casual)

What is 膝掛ひざかけけ?

膝掛ひざかけけ (ひざかけ) is a small blanket for your lap. Offices and cafes in Japan sometimes lend them out in winter or when the air conditioning is strong.

膝掛ひざかけけをお借かりできますか。 — Could I borrow a lap blanket? (polite)

Common mistakes

  • Using 足あし for the knee. 足あし is the leg or foot. Use ひざ.
  • Taking 膝ひざが笑わらう literally. It means shaking knees.
  • Reading 膝枕ひざまくら as ひざちん. It is ひざまくら.
  • Using 膝ひざを打うつ for injury. It means sudden understanding.
  • Always writing 膝ひざ in kanji. ひざ is common.

Practice

Try each answer before opening it. Questions 5 and 6 are a pair: an "aha" moment and a heart-to-heart talk.

1. Say "My knee hurts, so stairs are hard."

Show answer

ひざが痛いたくて階段かいだんがつらい。 — ひざ.

2. Say "The cat is sleeping on my lap."

Show answer

猫ねこがひざの上うえで寝ねている。 — ひざの上うえ.

3. Say "I fell and scraped my knee."

Show answer

転ころんで膝小僧ひざこぞうをすりむいた。 — 膝小僧ひざこぞう.

4. Say "He got down on one knee and proposed."

Show answer

彼かれはひざまずいてプロポーズした。 — ひざまずく.

5. Say "That explanation made me go 'aha!'"

Show answer

その説明せつめいに思おもわず膝ひざを打うった。 — 膝ひざを打うつ.

6. Say "Let's sit down and talk properly."

Show answer

一度いちど、膝ひざを交まじえて話はなそう。 — 膝ひざを交まじえる. This is the pair to question 5.

7. Say "After coming down the mountain, my knees were shaking."

Show answer

山やまを下くだりたら膝ひざが笑わらっていた。 — 膝ひざが笑わらう.

8. Say "I was tired and fell asleep with my head in my mother's lap."

Show answer

疲つかれて、母ははの膝枕ひざまくらで寝ねてしまった。 — 膝枕ひざまくら.

9. Ask politely to borrow a lap blanket.

Show answer

膝掛ひざかけけをお借かりできますか。 — 膝掛ひざかけけ.

10. How do you read 膝枕ひざまくら?

Show answer

ひざまくら — a lap pillow.

FAQ

How do you say "knee" in Japanese? 膝ひざ (ひざ).

How do you say "lap"? Also ひざ, as in ひざの上うえ.

What is 膝枕ひざまくら? Resting your head on someone's lap.

How do you say "kneel"? ひざまずく.

What does 膝ひざを打うつ mean? A sudden "aha" of understanding.

What does 膝ひざが笑わらう mean? Your knees shake from tiredness.

Vocabulary from this article

Tap the block to select all of it, then copy. In Anki: File → Import, note type Basic, separator Tab — the first column becomes the front, the second the back.

膝	ひざ — knee, lap
膝小僧	ひざこぞう — kneecap
膝枕	ひざまくら — lap pillow
ひざまずく	ひざまずく — to kneel
膝を打つ	ひざをうつ — to have an "aha" moment
膝を交える	ひざをまじえる — to talk closely
膝が笑う	ひざがわらう — knees go weak
膝掛け	ひざかけ — lap blanket
すりむく	すりむく — to scrape
階段	かいだん — stairs
曲げる	まげる — to bend

I'm Yuuki, a Japanese teacher based in Tokyo. I've taught on italki as a Top 1% teacher and watched over 1,500 anime. 膝ひざが笑わらう is one of those idioms learners love, because anyone who has climbed a mountain knows exactly what laughing knees feel like. For practice with feedback, Book a trial lesson · $13, or try the Japanese practice exercises first.

Sources: the author's own lessons and standard reference dictionaries.

More drills like the ones above, plus a timed JLPT-style mock test: Practice · N4 · Read something at this level: JLPT N4 stories with audio

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