Watch this girl walk. What is the most striking feature of her gait?
Is it the genu valgus? Is it her progression angle (or lack of?) Her Left sided increased arm swing? Her body shift to the left in Left stance phase?
We would like to discuss her progression angle. We remember that the progression angle is the angle the foot makes with the ground at heel strike and through stance phase (another way of describing it is, Are your feet turned out or turned in?). It is determined by many factors (forefoot position, subtalar joint angle, tibial abnormalities, femoral torsions, etc). In this case it is highly suspect that it is due to subtalar varum and internal tibial torsion, at least from what we can see and what we now without the advantages of an exam and clinical information. Lets now make this assumption and talk about it from this angle.
Tibial torsion is due to the development of the tibial shaft. It begins in utero, where most of us have tibial varum (due to intrauterine positioning), usually Left sided more than right (because most babies are carried on their back on the Left side of the mother and the Left leg overlies the Right in an externally rotated and abducted position.
At birth, we usually have a 5 degree toe in due to a 30 degree angle between the talar dome and head, which slowly decreases to approximately 18 degrees as we grow into adulthood, leaving us with a 4 degree toe out (still a fairly narrow progression angle). Meanwhile, the tibial plateau and malleoli are parallel at birth and the distal tibia “untwists” externally as we age (at a rate of about 1-1.5 degrees per year) till it reaches an ideal of 22 degrees in adulthood.
Over rotation of the distal tibia (relative to the proximal) results in external tibial torsion with a “toe out” or as it is referred to as, increased progression angle. Under rotation results in internal tibial torsion, or a “toe in”, also referred to as a decreased progression angle.
Some sources say that the development of the talus (angle between the dome and head) is largely responsible for foot position and progression angle. We think that careful measurement (looking at the transmalleolar angle, a topic for another post) reveals which it is, and in our experience, it is usually a combination of both (ie tibial torsion and talar development).
This video is an excellent clinical example of an in toed gait, a negative progression angle.
Ivo and Shawn…The Gait Guys….Yes, we are torsioned (or twisted as some may argue)….straightening out the facts so you don’t have to.