There is also another quite different theory as to why cats are kneading, that is that kneading originated back to the cats wild ancestors who had to tread down grass to make a temporary nest in which they could rest. When the cat kneads it presses downwards with it’s paw and exposes its claws. It closes it’s claws as it lifts the paw and the process takes between one and two seconds. Most cat owners see kneading as a problem, as it can be quite painful for the cat owner if the cat is kneading sitting in the owners lap.

Many cats purr when they are kneading, so this may be an indication that the cat is actually enjoying itself when kneading. This is the main reason why the first theory is the most likely one, and you can read about why do cats purr here.