Hinge joints swing back and forth like — well, a hinge on a door.

屈戍关节来回摆动，就像——嗯，门上的铰链一样。

These motions enlist the hinge joints. Similarly, my oval-shaped condylar knuckle joints allow my fingers to bend and ball up for a good fist pump.

同样，我的椭圆形髁关节允许我的手指弯曲并向上握出一个好的拳头。