How do you measure tibial torsion anyway?
With all the talk on the Crossfit blog about the knees out debate, we though we would shed some light on measuring torsions, beginning with tibial torsion, since this does not seem to have been taken account of in the discussion and we feel it is germane.
Looking at the top left picture: we can see that the axis of the tibial plateau and the transmalleolar axis (an imaginary line drawn through the medial and lateral malleolus) are parallel at birth (net angle zero) and progress to 22 degrees at skeletal maturity, resulting from the outward rotation of the tibia of about 1-1.5 degrees per year. This results in a normal external tibial version of about 17-18 degrees (you subtract 5 degrees for the talar neck angle, talked about in the link above). Note that this is the normal or ideal angle we would expect (hope?) to see. Go 2 standard deviations in either direction and we have external and internal tibial torsions.
You can go about taking this measurement in may ways; we will outline 2 of them.
- In the upper left picture, we see an individual who has their knee flexed to 90 degrees over the side of a table while seated. This represents the tibial plateau angle. You the use a protractor to measure the angle between the tibial plateau and an imaginary line drawn through the medial and lateral malleoli. This is the transmalleolar angle. You then subtract 5 degrees from this number (remember the talar neck angle?) to get the angle of tibial version (or torsion).
- In the lower left and right pictures, we have the patient supine with the knees pointed upward and tibial plateau flat on the table. Then, working from inferiorly, use a goniometer to measure the angle of the transmalleolar axis. Again, we subtract 5 degrees for the talar neck.
We would encourage you to read up on torsions. This post, which we wrote over a year ago, is probably one of the most important ones on tibial torsions.
Torsions. Important stuff, especially when you are talking about the axis of the knees in activities like a squat. Remember, the knee is a hinge between 2 multiaxial joints (hip and ankle) and will often take the brunt of the (patho)mechanics, as it has fewer degrees of freedom of movement. If you have external tibial torsion and you push your knees (angle your feet) out further, you are moving the knees outside the saggital plane. You have better have a very competent medial tripod! If you have internal tibial torsion, angling the feet out may be a good idea. Know your (or your patients/clients/athletes) anatomy!
The Gait Guys. Bald, Good Looking and Twisted. Here to help you navigate your way through better biomechanics.