Equilibrium situations in bend force systems

This article provides a simple theoretical approach to the equilibrium situations encountered in biomechanics. Basic differences between the moment of a force and the moment of a couple are described. The concept of the center of resistance is defined and applied to the case of a force system (Rs). Three equilibrium situations are schematically described: the off-center V bend, the centered V bend, and the step bend. Two clinical examples are detailed (one from the Begg technique and one from the Ricketts technique) to demonstrate clinical applications of force in these three situations.