1.knee的基本意思是“膝盖”,指大腿与小腿连接处的前面。引申可指“裤子的膝盖部”。
2.在表示“跪着,屈膝”时, knee常用复数形式。
3.在表示“在…的膝下”时,通常用at sb's knees结构。

be〔go〕 (down) on one's knees
跪下,跪着 kneel or be kneeling, especially when praying or showing that one accepts defeat
The boys were on their knees for hours, begging their parents to let them go on the trip.这些男孩跪了好几个小时,恳求父母同意他们去旅行。
She went down on her knees to pray.她跪在地上祈祷。
They went down on their knees and kowtowed.他们跪下并磕了头。

bring to one's knees
迫使某人屈服 force sb to submit
▲bring sb to one's knees
Nothing could bring us to our knees.什么也不能使我们屈服。
The country was almost brought to its knees by the long strike.因长期罢工,这个国家已濒临崩溃的边缘。

His knee was his vulnerable spot.他的膝关节易受伤。
How did you get that scrape on your knee?你膝盖上的擦伤是怎么弄的?
She fell down and cut her knee.她跌倒了,摔破了膝盖。
She sat with her child on her knees.她把孩子放在腿上坐着。
He got down on his hands and knees to crawl under the table.他双手双膝趴在地上,钻进桌底。
You'll have to eat your dinner off your knees,I'm afraid!对不起,这顿饭你只好把餐具放在腿上吃了。
He started to get up, but his knees gave under him.他开始站立起来,但两膝发软,站立不住。
His knees knocked together.他吓得两膝发抖。
He leaned forward, his elbows on his knees.他屈身向前,两肘支在膝盖上。
He got the knee in the face as he tried to get up.他试图站起来时脸部被人用膝盖撞了一下。
These trousers are torn at the knee.这条裤子的膝部破了。

［词源］  ＜古英语cneow,与古高地德语kneo(膝,膝盖)