Elastic yarn is incorporated in different manners in two circumferential sections of the ankle and arch portions of the sock to provide compressive force and support to these areas of the wearer. The elastic yarn is incorporated in spaced-apart wales of each course of the ankle and arch portions and is floated inside of plural wales in the rear half of successive courses in the ankle and lower half of the arch to form mock ribs extending around substantially the rear half of the sock. The elastic yarn is incorporated in every other wale of single alternating courses and in the remaining wales of single intervening courses in the front half of the ankle and upper half of the arch to form a diamond pattern extending around substantially the front half of the sock. By incorporating the elastic yarn in two different manners in every course, the proper amount of compressive force and support is provided on the ankle and arch of the wearer.