Foot Varus is a developmental deformity, an ankle deformity caused by spasm of the posterior tibial muscle that can be found when a child is born. Foot varus can occur on one foot or on both feet. During development, due to the failure of the development of the tendons and ligaments (posterior and deep) of the foot, it fails to keep pace with the development of other tendons and ligaments of the foot. The consequences It is these tendons and ligaments that pull the posterior medial side of the foot downward, causing the foot to twist downward and inward. As a result, the bones of the foot are in an abnormal position, and the foot is inverted, stiff, and cannot return to the normal position.