In most people, ligaments (which are the tissues that connect bones to each other) are naturally tight in such a way that the joints are restricted to 'normal' ranges of motion.

If muscular control does not compensate for ligamentous laxity, joint instability may result.

The trait is almost certainly hereditary, and is usually something the affected person would just be aware of, rather than a serious medical condition.

[1][2] Ligamentous laxity may also result from injury, such as from a vehicle accident.

Ligamentous laxity will show up on an upright magnetic resonance imaging (MRI), the only kind of MRI that will show soft tissue damage.