PHYSIOLOGICAL BOWING IN CHILDREN - AN ANALYSIS OF THE PENDULUM MECHANISM

Prompted by common observations, we investigated why physiologic bowin g occurs in infants and what purpose is served by its characteristic v arus to valgus to neutral movement of the mechanical axis of the knee which we term ''pendulum-like swing'' in the frontal plane. Anthropomo rphic data were readily available on age-related increase in weight, f emoral and tibial lengths, and changes in lower extremity to allow con struction of an ''average'' leg representing ''normal'' limb alignment of a growing infant male aged 1-8 years. This enabled us to calculate the bending moments on five anatomic levels of the limb about the kne e; more important, during some growth periods the bending moments are minimal and may be used to diagnose pathologies of the lower limb. Thi s form of analysis may prove useful in pathologies in which mechanisms serve to ''mask'' problems diagnosed on the basis of knee angle alone . When the child begins to stand, the pendulum mechanism is needed to equalize physeal growth about the knee.