Biomechanical Dysfunction
Biomechanical dysfunction is commonly caused by two factors:
A) The Tibial Varum Factor
B) Biomechanical Deformity Factors
This guide does not cover biomechanical dysfunction caused by Biomechanical Deformity Factors.
Excess Pronation
The most common side effect to A) The Tibial Varum Factor and B) Biomechanical Deformity Factors is excess pronation. Excess pronation is generally the symptomatic compensation for these ossesous anomalies. Excess pronation at the subtalar joint commonly exhibits:
- Calcaneal eversion
- Internal tibial rotation
- Lowering and elongation of the arch structure
- Excess medial lower limb strain
- Excess lateral upper limb compensation
- Medial plantar displacement of the talus upon the calcaneus
- Excess weight bearing over the 1st metatarso-phalangeal joint
How Tibial Varum Causes Excess Pronation
The normal lower limb (A) is represented by a 3-4 degree tibial varum angle and will strike the ground on the outside edge of the foot. However, when approaching hard flat ground the foot must compensate by pronating excessively at the subtalar joint to gain ground contact (B). If the normal foot type (A) was standing on a softer surface like natural ground, then the ground would give-way to accommodate for the foot position. Hence forming a natural footprint which prevents excess pronation similarly to an orthotic. Remember your footprint when you last walked on the beach? You will notice that the sand gave way under the lateral strike of your heel forming a natural wedge. Thus preventing excess subtalar joint pronation from occurring.Therefore, the greatest cause of compensatory excess pronation is the natural tibial varum angle combined with unnatural hard flat surfaces.