Knee adduction moments

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Good evening.
Still learning as I go. I understand the concept of a knee adduction moment as seen in varum and therefore understand the efficacy of lateral posts to offload medial knee OA..... even if this needs to be done with medial rear foot support to maintain a functional foot.
I use lateral postings and heel raises with moderate arch fills for those with a propensity to lateral ankle sprains/cuboid/supinated feet shiz however.... I note that many supinated feet come with valgum knee types. Questions are:
- has any one else noticed supinated feet often corresponding to knee valgum.
- could the knee deformity be explained by lateral STJ axis during development or incidental.
-is their such a thing as a knee abduction moment and what is the intermediate to long term risks of laterally posting feet with knee valgum. Is there the same risk of lateral knee compartment issues be it meniscus or OA as a consequence of this prescription.
I tend to prescribe aggressive glute strengthening aimed at external hip rotation to counteract the lateral posting in these people however I'm not sure if I'm overthinking or off the mark in this regard.
Any answer gratefully received
Appreciate your time

 

or it could be that the genu valgum causes the foot to supinate and develop at lateral STJ axis over time
See this thread:
https://podiatryarena.com/index.php?threads/does-genu-valgum-cause-the-foot-to-pronate.1289/

 

ABduction and ADduction moment are all an alignment problem. We are doing free body diagram analysis here and when doing that you have to carefully define what object your are talking about. This is why I'm talking about moment on the lower leg rather than moment on the knee. When the center of pressure on the top of the tibia is lateral to the center of pressure under the foot (genu varum) you will have an external lower leg adduction moment. (Draw the lower leg and the arrows from body weight applied to the top of the tibia and ground reaction force under the foot) To maintain equilibrium, (prevent the lower leg from adducting) there has to be an internal abduction moment from the structures of the knee. The structures at the knee that create the internal abduction moment (resisting the external abduction moment) are increased compression of the medial compartment and tension in the lateral collateral ligaments.

When the forces (body weight on top of the lower leg, and ground reaction force under the lower leg) are not aligned the distance between the line of action of the two forces is proportional to the magnitude of the moment. So the goal of treatment is to make the line of action of the forces closer together and one way of doing that is shifting the center of pressure under foot. This is what a lateral wedge does.

With genu valgum, you get the opposite of the above. Just draw the picture.


Pronation and genu valgum: With pronation of the subtalar joint you can have the center of pressure under the foot anywhere depending on the range of motion of the subtalar joint. When a subtalar joint runs out of range of motion before the medial forefoot hits the ground this will cause the center of pressure to be under the lateral side of the foot. (A foot, in Root theory, that has a partially compensated varus, either forefoot or rearfoot). This will tend to create an abduction moment on the lower leg. An abduction moment on the lower leg will tend to create a genu valgum. Treat by shifting the center of pressure more medially with a varus wedge.