The dangers of flat feet include pain in walking, swelling of the joints, and abnormal gait. The use of foot pads to support the soles of the feet in patients is a common non-surgical treatment to make the joints better. Bone reconstruction surgery, such as subtalar joint reconstruction, can also be performed for patients who do not benefit from non-surgical treatment. The hazards of flat feet include walking pain, which usually occurs in the medial plantar area and worsens after prolonged standing or walking; pain in the navicular tuberosity; the abnormal gait of a figure of eight when some patients run; and heel valgus, which greatly affects the appearance of flat feet. Therefore, it is best to detect and treat flat feet as early as possible, and both adults and children should actively consult hospitals after the discovery of flat feet, so as to clarify the cause of the disease and to prevent more serious bone and joint lesions that may occur.