As a foot flattens out on the ground, supporting tissues that run along the bootom of the foot (the plantar fascia) are stretched. If these forces are excessive they can lead to stress and inflammation of the tissues, causing pain under the heel when weight is placed on the foot.
KNEE PAIN
As the foot flattens out on the ground, the leg turns slightly to follow the movement of the foot. If the movement of the foot causes the leg to turn further than the knee can comfortably accommodate, the resulting forces on the knee may lead to stress and pain.
BACK PAIN
As the foot flattens, legs turn inward. Excess inward turning of the legs put stress on the bones in the hip, pelvis and lower back region causing pain and stiffness in the lower back.