knuckle arm

例句：

1. 1. He used toplay football with his friends on theknuckle of his arm.
   他以前用肘部和朋友们踢足球。
2. 2. Sheswung her arm around and caughta ball.
   她挥动手臂接住了一个球。
3. 3. The doctor advised him to exerciseregularly to maintain his knucklearm strength.
   医生建议他定期锻炼以保持肘部力量。