Participants with flat foot unilaterally (Only one foot's Calcaneal pitch angle ≤ 20 degree)

Participants with flat foot bilaterally (Both feet's Calcaneal pitch angle ≤ 20 degree)

Calcaneal pitch angle (CPA) is defined as an angle between a line drawn from the inferior of the calcaneocuboid joint to the inferior border of the calcaneus and a second line drawn from the inferior aspect of the sesamoid bones to the inferior border (13). CPA for both (right and left) foot was evaluated from all plain radiographs in this study and the angles equal to or less than 20 degrees were accepted as a flat foot.

Pelvic obliquity (PO) was measured by horizontal pelvic obliquity according to Osebold et al. from a posteroanterior radiograph. The angle between the line drawn between the most proximal points on the iliac crest and the line drawn parallel to the lower end of the radiograph was recorded.

The Cobb angle (CA) is a gold standard measurement for identifying the magnitude of spinal curves (14). Spinal curvature was measured from the standing full-length posteroanterior radiograph. The angle of the curve is measured as an angle between the perpendiculars of the lines parallel to the upper border of the upper vertebral body and parallel to the lower border of the lowest vertebral body of the curve (16). Straight or symmetrical spines in the coronal plane were accepted as a normal spine, and curves<10 degrees accepted as spinal asymmetry, and the curves ≥ 10 degrees accepted as scoliosis (15). Spinal curve patterns in coronal planes were classified according to the Scoliosis Research Society classification. The curve was classified as single in terms of one curve exists in the thoracal or lumbal spine; as double in terms of one curve exist the through thoracal and lumbal spine; and as triple that exists through upper thoracal, middle thoracal and lumbal spine (17).