Updated: Dec 26, 2020
If you're familiar with social cats, then you experienced them finding a soft service to make some bread on. Cats will knead their owners, soft blankets, pillows, other cats, other dogs, or even the air. Upon veterinary research there are several theories as to why cats knead:
It's due to the motion they made with their paws on their mother's stomach while nursing. This would stimulate milk production and flow from the mother's nipple. This positive association is why they have carried it to their adulthood;
Kneading was passed down from their ancestors. They would do this to inspect vegetation and create a soft resting space for birth;
A means of stretching their muscles;
A way of using scent glands on their paws to release pheromones to mark their territory;
A mating call from female cats in heat to male cats.
The truth of the matter is that we will never truly know why this phenomenon happens. What we do know is that most cats may make the same synchronized motion with their paws, while kneading, but it can differ. Some may accompany their kneading session with a loud or soft purr, some may knead in silence, some may arch their back, some may suckle or bite, and some may even extend their claws. The way a cat kneads reflects their individual character and personal preference.
Kneading is a natural behavior for cats, and when you are able to experience this with your cat you are also strengthening your bond. So if your cat is anything like mine, take a deep breath and sit through the pain of their rhythmic claw extension (if it's too much grab the nearest soft blanket and join the knead session).