a condition in which someone is able to move and bend their joints (= places where bones join such as in your fingers, at your knees, etc.) more than is usual

This is a genetic condition affecting collagen (a basic building block of the body), which then causes hypermobility of the joints. 这是一种影响胶原蛋白（身体的基本组成部分）的基因状况，会导致关节过度松弛。

For most children these muscle cramps are due to hypermobility - excessive suppleness or being "double-jointed". 对于大多数儿童来说，这些肌肉痉挛是由于关节过度松弛造成的，即关节过度柔软或 "双关节"情况。