A dog’s hind legs often move or twitch when they are petted in certain spots.
It is the same reason some people get shivers when someone touches their back or shudder when fingernails are scraped down a chalkboard.
It’s a reflex.
It’s kind of like when the doctor hits you on the knee with his rubber mallet and your leg kicks, same reflex.
Most vets agree that spinal nerves pass all the way to the abdomen, and scratching the area around the nerves causes a feeling of itching.
Some experts say it’s a method that dogs’ wild ancestors once used to scare away predatory animals looking for a dog-sized lunch.
Others say it’s there to keep a dog from drowning.
The area on a dog’s body that is is most sensitive is often referred to as the “saddle region.”
The hind leg movement that occurs when rubbing or scratching a dog in the saddle region is called the “scratch reflex.”