knuckles

Charlotte rapped on the window with her knuckles.

夏洛特用指轻敲着窗户。

He got a rap over the knuckles for spending too much money on his business lunches.

因为在商务午餐上花钱太多，他挨了一顿批评。

Our fingers bend at the knuckle.

我们的手指在指关处。

The most common type of joint in the human body is the diarthrodial joint -- knuckles and shoulders are examples -- in which two bones come together in a capsule.

体中最常见的关是运动关，如指关和肩关等，关处的一个囊状物把两根骨头结合在一起。