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Average Torsion Axis Location of Athletic Movements: Subject Specific or Movement Specific?
Graf ES, Stefanyshyn DJ.
J Appl Biomech. 2012 Aug 22.

 

this might help to visualise the axis of interest





Dave Smith

 

There are many joints between the two markers and the found axis of motion has contributions from each of those joints. An analogy: You can create an axis of motion between the distal phalanx of your index finger and your arm. That axis of motion may not tell you much. I'm not saying that finding this axis of motion in the foot is useless, but there is more work to be done to show that this axis is useful. It's the forces, not the motions that are important.

Eric

 

The "torsion axis" as these authors describe, is not the subtalar joint axis (as suggested by Admin 2's posting). Rather, the "torsion axis" would be more closely related to the midtarsal joint axis, not the the subtalar joint axis.

This "torsion axis" may be useful to study but, unfortunately, will likely be greatly affected by skin to bone motion and also represents the combination of motions at the midtarsal joint, cuboid-metatarsal joints, navicular-cuneiform joints, cuneiform-metatarsal joints and the bending of the metatarsals during weightbearing activities. My belief is that since this "torsion axis" involves multiple joints, it will be very difficult to use it in a clinical setting.

I also think it would be more helpful to call this "torsion axis" the "rearfoot-forefoot axis" or the "midtarsal-midfoot joint axis" to avoid confusion.

 

Thanks for the picture Dave. Can anyone share that paper with me please?

If the axis of the paper corresponds to the picture above I think this are may have great importance in understanding and treating foot and lower limb dysfunction. This area seems to correspond to the are on F/T curves where we intitially see a delay in the rear foot un-weighting. This corresponds to issues from AJ equines, opposite side limb length being short, and potential dysfunction in the 1st mpj.

I think the equinus issues are probably the most important here, but time will tell.
sincerely;
Bruce

 

Did you mean this one attached

 

David;
actually no, I meant this one:
Average Torsion Axis Location of Athletic Movements: Subject Specific or Movement Specific?
Graf ES, Stefanyshyn DJ.
J Appl Biomech. 2012 Aug 22.

Thanks though, I will work thru that paper you included. You are a gentleman and a scholar sir!
Bruce