If you can, you might be what some people call "double-jointed." But, a Moment of Science wonders, how could anyone have double joints?
如果你能做到，那么你可能拥有双关节。但是，《科学一刻》想知道，一个人怎么可能拥有双关节呢？
2
The utility model discloses an upper circular cone double-jointed translational artificial lower limb connecting fitting that pertains to the fixed connecting fitting.
本实用新型公开了属于固定连接件的一种上圆锥筒双接头平移下肢假肢连接件。
3
Ligaments and tendons usually restrict the movement of the joint, but in some people, these normally restrictive tissues can be quite flexible and allow the extra movement we call "double-jointed."