Cut the tripe into small squares and put them into a large pan with the veal knuckle; cover with the water and bring to a boil; lower the temperature and simmer, uncovered for about 2 hours, or until the tripe and knuckle are just tender but not too soft.
Meanwhile, roast the chilies by placing them in a 350 degree oven until skins are browned or blackened, turning them once; place them in a bag to steam until cool enough to handle.
Peel and cut the chilies open and remove seeds and the veins; cut into strips.; add to the meat while it is cooking.
Remove the knuckle and allow to cool enough to handle; strip off the meat; chop roughly and return them to the pan.
Pour in the hominy.
Simmer the menudo slowly, uncovered, for an additional 2 hours.
Add salt to taste.
Sprinkle with oregano and serve in large, deep bowls.