1、knee指生理上的膝盖。
2、lap指膝盖周围的空间，一般不单独指称生理上膝盖。
knee，英语词汇，基本释义为膝关节、膝、膝盖。
参考例句
The knee jerk is a typical respondent.
膝反射是一种典型反射。
To scratch the back while the knee is itching—irrelevant.
膝痒搔背。
The little boy behaved bravely after he hurts his knee.
小男孩膝盖受伤后表现地很勇敢。
They had to wade knee-deep through mud and debris to reach the victims.
他们须通过齐膝的烂泥和堆积物,磕磕绊绊来到遇难者身旁。
There was an even more pronounced link between regular dancing in three-inch heels and a reduced risk of knee problems.
研究者们甚至发现经常穿三英寸高的高跟鞋跳舞明显和降低膝盖得病的危险有关。
参考资料：百度百科-knee
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