Their knees were touching ...是什么意思？

Their knees were touching ...

他们的膝盖挨着。

their

pron. 他（她，它）们的，在提及性别不详的人时，用以代替 him 或 her；

例句
Their permissiveness toward their children reflects the wild abandon of their own lives.
他们对孩子的放任折射出他们自身生活的放浪形骸。

knees

n. 膝( knee的名词复数 )，膝盖，（裤子的）膝部，坐下时)大腿朝上的面；

例句
We beg the Government on bended knees not to cut this budget.
我们恳求政府不要削减这项预算。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

touching

adj. 令人同情的，感人的，动人的；prep. <书>关于，至于；v. 接触(touch的现在分词)；

例句
...a touching elegy for a lost friend.
致亡友的感人挽歌