The condition of having an asshole itch so intense and deep that it feels like the only way you can properly scratch it is to stick your finger up your ass all the way up to the knuckle, and scratch your asshole from the inside.
A case of knuckle ass might be the result of poor hygiene (see hanus anus
) or could just be an unlucky ass itch that anyone can get from time to time.
"I took a shit this morning and I guess I didn't wipe well enough. Now I've got major knuckle-Ass"