finger knuckle

例句：

1. 1.She uses her fingers to pick up the pen from the desk.
   她用手指拿起桌上的笔。
2. 2.The artist used his fingers to paint the picture.
   艺术家用手指画这幅画。
3. 3. He pointed to the finger on his left hand.
   他指向他左手上的一根手指。