While there certainly are gymnasts, rhythmic gymnasts, contortionists and individuals who are extremely flexible, calling them double jointed, is not really a good way to describe their exceptional flexibility or to identify them as highly flexible individuals.

Their Body Structures are the Same as Other Normal Humans

Extremely flexible people do not have “two joints” nor do they have any other major physical or bone structural differences from other human beings. There are a number of potential hereditary factors, that may explain their increased natural flexibility, but none of those has to do with having extra joints or any other completely different body or bone structure.

Physical Explanations for Exceptional Flexibility

In a person of exceptional flexibility, you may find that their joints may not be supported firmly or strapped tightly by connective tissue. Certain bone conformations and formations may allow greater movement of joints. These are all hereditary characteristics that can result in such considerably greater range of movement (ROM) for these certain individuals.

Loose-Jointed is a Better (and Yet Worse) Term

The joints of an extremely flexible person can be so loose, in their articulation (the point at which two bones make contact), that joint stability is actually substantially lacking. And such loose-jointed gymnasts or individuals are, often therefore,  significantly more prone to dislocations and other injuries to the joints, when training, competing or subjected to heavy stresses on their joints.

Too Much Flexibility for Artistic Gymnastics?

Because of this extra potential for injury, such a loose jointed condition is not necessarily good for athletes who are competing in artistic gymnastics. Tumbling, vaulting and dismounts from apparatus put considerable stress on the joints of the body of any gymnast.  Any extra looseness of joints and susceptibility to injury is more of a liability than any gains in the execution of flexibility skills may be worth.

Extra Strength Training

It is possible, that for some naturally loose-jointed body configurations, that extra strength training, specifically weight training, may be of use in countering the problems. This may not work in every situation, but extra strength training, for individuals with these conditions is usually necessary anyway, since they are often considerably naturally less strong than the average gymnast. Some gymnasts, however, may develop more rapid muscle fatigue than normal since their muscles must sometimes work harder to compensate for the excessive weakness in their ligaments.

Want to Appear Informed?

If you wish to appear like you know what you are talking about, you will want to refer to extremely flexible people and gymnasts as:

• Extremely flexible
• Having hypermobility
• Loose-jointed

or even:

• Contortionists
• Rhythmic gymnasts

But to call gymnasts or other extremely flexible people double-jointed, while a common enough phrase is incorrect.