The bowed appearance of the lower extremities is most often caused by internal rotation of the tibia in relationship to the femur. It is most commonly seen as the infant commences ambulation. This so-called physiologic bowing usually spontaneously resolves with growth and the maturity of the lower extremities. In older children, tibia varum may occur, in which there is a local arrest of growth on the posterior medial aspect of the tibia producing a true structural angulation. In certain long-standing metabolic or genetic bone disorders, the effects of weight bearing produce a true bowing of the extremities with changes about the hips, knees, and ankles. The most important aspect in the evaluation of a child with a bowed appearance of the lower extremities is to determine which conditions require aggressive treatment and which ones require simply giving the parents reassurance that the condition will spontaneously regress.