'Genu valgum', commonly called 'knock-knee';, is a condition in which the knees angle in and touch one another when the human leg is straightened. Individuals with severe valgus deformities are typically unable to touch their feet together while simultaneously straightening the legs. Mild genu valgum can be seen in children from ages 2 to 5, and is often corrected naturally as children grow. However, the condition may continue or worsen with age, particularly when it is the result of a disease, such as rickets or obesity. Idiopathic genu valgum is a form that is either congenital or has no known cause. Other systemic conditions may be associated, such as Schnyder crystalline corneal dystrophy, an autosomal dominant condition frequently reported with hyperlipidemia.