The main function of the foot internal arch (Medial Longitudinal Arch) is to extinguish the inertia forces and to decrease substantially velocity of the leg movement which is developed during step period. Note that if to walk with velocity 4-5 km/hr, your foot touches the supporting surface with velocity 50-60 km/hr. To decrease this value to zero before the second leg begins to move, the braking distance is needed, i.e. high clearance (air-gap) under internal arch. Not considering this nature-provided wise instrument, the orthopaedic specialists eliminate air-gap under arch with the rigid orthotics. Unfortunately, this is world-wide practice.
But the chain of mistakes is not ending here. When there is a question about amortizing function of the arches, extinguishing of vertical velocity for General Centre of Gravity is considered. Such type of movements’ kinematics corresponds with functioning of external arch and transversal arch. On the foot imprint we observe that the load is shifting from the heel-bone centre to external side, to the apex of internal arch. It is because internal arch is rotated in subtalar joint. The arch is “falling” with respect to support point in the direction of heel-bone. Movement trajectory for arch apex is directed not straight down but along the radius. It can be clearly seen on the photo. On the level below ankle, foot is turned inside.
Internal arch gained support, hence callous tissues are in this place. Dynamics of arch’s height decreasing (pronation) is very important for all structures of human organism. This decreasing contains following functions:
– Compensate the difference in lower limbs lengths
– Safeguard the vertebral column and brain from shocks (by extinguishing inertia forces emerging under movement condition from (5-20)g to 0.5g)
In all cases of internal arch pronation it is necessary to define right underlying reasons. Otherwise it is not possible to return subtalar joint into its original position. In all cases feet deformations take place under the load impact, i.e. General Centre of Gravity is shifted with respect to the foot support points. Pronation of internal arch is observed under following conditions:
1. If there is difference in the lower limbs lengths, and heel-bone is turning (valgus-effect ).
2. If the support point appears under external arch when this arch is deformed, or similar to what is going on in walking process – arch apex lies flat on the supporting surface.
3. When each foot turns outside (toes first) in standing position and while walking.
All three of these unfortunate conditions are successfully eliminated by hydrostatic method, when standing on the podocorrectors projection of body’s General Centre of Gravity coincides with centre of support feet triangle. This means that functional and anatomical difference in lower limbs lengths is compensated. This is approach when the body’s General Centre of Gravity and muscles tone are considered, when system gains the balanced stable condition. With such approach the pump function of the muscles is quickly restored.