"...not everybody keeps their genitals in the same place."
The genitals are the reproductive organs in most humanoid species.
In males, the testes are very sensitive to pressure. A sharp blow to the organ can render Humans and aliens helpless.
In at least one species, the genitals are located in the right knee. This is different from many other species. This did not however, affect the sensitivity of the organ. (Star Trek VI: The Undiscovered Country)