Flexural limb deformity occurs in two forms. The first form, also known as contracted tendons, clubfoot, or knuckling, is the inability to extend a limb fully. The condition may be present at birth (congenital) due to improper positioning in the uterus (which can lead to dystocia in the mare), abnormal fetal development, disease or malnutrition in the dam; or acquired as the result of nutrition (abrupt changes in amount or quality of feed leading to rapid growth), polyarthritis, trauma, or disease. It is a common condition in foals, usually occurring anytime from birth to 14 months of age.