knuckling

Charlotte rapped on the window with her knuckles.

夏洛特用指轻敲着窗户。

Our fingers bend at the knuckle.

我们的手指在指处弯曲。

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，他挨批评。

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.

人体中最常见的是运动，如指等，处的个囊状物把两根骨头结合在起。