Walking has been called a sagittal plane activity. Clearly all three planes are involved, but the greatest joint range of motion (ROM) and the line of progression occur in the sagittal plane. To maintain a flowing and steady forward motion, there is a critical dependence between all the major joints of the lower limb. We can appreciate that without motion at the hip, walking would be very difficult. Knee flexion is essential for ground clearance and forward progression without hip circumduction. Motion at the ankle joint allows the body weight to pass uninterrupted directly over the plantigrade foot. In midstance, the foot acts as a stable anchor to everything above it, and then rapidly transforms into a versatile hinge as heel lift occurs and the opposite limb swings forward. But there is one final joint upon which each of these depends. It is not surprising, if you follow the sequence of events from hip to knee to ankle, to recognize that the most distal joint can have the greatest impact on all of those above it.