In a mixing bowl, stir together the mayonnaise, sour cream, Worcestershire sauce, Knorr seasoning, salt and pepper until well combined. Fold in the spinach, water chestnuts and green onions until evenly mixed. Cover and chill for at least 2 hours or until ready to serve.
1 cup mayonnaise, 1 ½ cups sour cream, ½ teaspoon Worcestershire sauce, 1 1.4-ounce package Knorr vegetable recipe mix, ½ teaspoon salt, ¼ teaspoon black pepper, 1 10-ounce package packed frozen chopped spinach, drained, 8 ounces canned water chestnuts, drained, 2 tablespoons green onion, minced