词汇点睛
knee n.膝;膝盖;膝关节
[观察]
My hand and knee were bleeding.我的手和膝盖在流血。
His left knee was hurt in a traffic accident.他的左膝在一次交通事故中受伤了。

在表示“跪着;屈膝”时，knee常用(单/复数形式。表示“在某人的膝下”时,通常用at sb's knee Go down on your knees!跪下!