All joints have a natural range of motion with the muscles and tendons that bind them in place. These ranges of motions can be expressed as norms in the human population.

These ranges also reflect the actions these joints are put though. If you straighten a leg at the knee, you don't expect it to go past that angle, since it would not benefit the normal uses you have for you legs.

Overextensions come in three forms; Genetic, recovery, and trained.

Genetic over-extension happens because of the type of collagen present in connective tissue. There are already multiple varieties of collagen present in the body, each with it's use. Sometimes, Ligaments have a variant collagen that allows them to stretch longer than the general population. In some cases this is referred to as ehlers danlos syndrome, depending on how prevalent the mutation is. Basic advice is to intentionall develop strength and fine motor skill with the associated joints, so the affected person is less likely to accidently put themselves in a dangersous situation.

Recover over-extension is the result of a previous injury - The body can heal on the micro level, but on the macro level surgical intervention bay be necessary to make sure things heal in previous orientation and lengths.

Trained over-extension is due to the fact with repeated training, the automatic reactions of the body can be relaxed, essentially putting the well trained body under intentional control. This is usually more of a side effect of training (either the result of training, or the main push of training is not that effect).

All over-extensions should be seen as potentially more dangerous than the normal range of motion, and should be handled with care.

Compare with Dislocation