knuckle radius

例句：

1. 1. The doctor measured the knuckle radius of my hand to determine if I had arthritis.
   医生测量了我的手指关节半径，以确定我是否有关节炎。
2. 2. He was trying to find the knuckle radius of the door to open it.
   他试图找到门的关节半径来打开它。
3. 3.The knuckle radius is an important factor in determining how well a person can grip objects.
   关节半径是决定一个人能否紧握物体的一个重要因素。