The Criteria Of Normalcy

When the podiatrist performs a biomechanical assessment, he has in his mind a model of what should be a normal foot. This is how we recognise when we see abnormality. It is a known fact that most of us have some sort of deviation from the norm, the statistics have shown that up to 85% of us are not perfect as far as our feet are concerned. However whether one has symptoms or not depends on a combination or variety of factors.

We look at:
  1. the alignment of the leg to the ground, it should be nearly straight. The most common deviation is Tibial Varum, which is a curvature in the leg bone leading to an excessive lateral heel strike (outerside of the heel).
  2. the alignment of the heel to the leg, this is the relationship of the calcanues and talus to the leg. It should be about 2 degrees inverted, but it is commonly inverted by 4 degrees and more and this leads to an inverted heel strike. Deviation is referred to as Rearfoot Varus.
  3. the alignment of the forefoot the the rearfoot, the should be no deviation of the forefoot to the rearfoot, although it is common to have a forefoot that is inverted to the rearfoot leading to a foot that pronates (rolls in) excessively. Deviation is referred to as Forefoot Varus or Forefoot Supinatus
  4. The position of the rearfoot to the ground on standing, should be vertical. Referred to as Rest Calcaneal Stance Position.
  5. The flexibility of the calf muscles, that allows the foot to dorsiflex, or allows the leg to move over the foot during normal walking. Most people present with tight calf muscles. Normal measurement would be +10 degrees dorsiflexion on the leg. This is referred to as Ankle Equinus.
  6. Leg length Discrepancy, the legs would be measured and should be of equal length.
  7. Range of motion of the Sub-Talar Joint, dictates how much movement there is in the ankle on Inversion and Eversion.

The range of eversion is vital when determining whether the patient has used up all the motion or not during foot movement. Once a foot is fully pronated or everted in the Sub-Talar Joint, other joints like the Mid-Tarsal Joint will come into play as a way of compensating further. This can lead to numerous foot problems.