Contrary to misconception, the lower leg is not perpendicular or at 90° to the surface we walk on.  In almost every person there is a tibial varum angle of between 4-6° to the vertical in the average lower limb, ie. it is slightly bowed (in some cultures this angle can be heightened).

There are generally 3 types of leg types prevalent in human beings:

1. Straight
2. Knock Knees
3. Bow Leg

In addition to the type of leg, each of these types can have a "torsion out", "torsion in", "no torsion" or a combination of all three!

The tibial varum angle is an element that allows the leg, when it is correctly aligned in the neutral position (N.C.S.P. - Neutral Calcaneal Stance Position), to exhibit a natural inverted position to the ground.  When we walk on soft surfaces the ground gives way to "accommodate" the foot structure and its action of striking laterally (due to the action of the tibial varum element), however, when we walk on hard surfaces our lower limb biomechanics accommodate with shock absorption and collapse (excessively pronate) to allow contact and ultimately "toe-off" to occur.

The normal lower limb is represented by a 4-6° tibial varum angle.  The normal/average lower limb forms a 4-6° curve from the vertical and is "mildly bowed".  this is why, when the foot is correctly aligned at neutral to the leg, it forms a natural inverted position to the ground.

Content & Images © 2006 Footsteps Orthotics Pty Limited