Genu valgum is a deformity of the bones in the lower limbs characterized by the knees which angle in: commonly called knock-knee. The knees point inward and touch: the legs seem to form the letter X or the symbol )(. There are many possible causes: genetic deformity, bone disease ... If the genu valgum is minor, it is not always necessary to correct it, because only very severe deformations prevent the patient from walking properly. Treatment is most often to wear orthopedic shoes, but surgery is sometimes necessary to remove part of the bone (osteotomy), and make realignment of the legs possible. On the other hand, some genu varum occur pointing out, where the legs seem to take the form of two brackets: ().