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STJ motion, stupid question

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Robertisaacs, Mar 26, 2008.

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    I wish / need to avail myself of the knowledge of the community. Specifically the bit where Kevin said there was no such thing as a stupid question.

    I'm still trying to generate that 3 dimensional model for transfer of rotational force from the hip rotators to the frontal plane of the foot. Cheers sam. :mad::butcher: Its like beating myself with a hard stick.

    Grazing through the literature on STJ motions i found this graph.


    Mcpoil & Crnwall Journal of the American Podiatric Medical Association Volume 92 Number 2 67-76 2002 Motion of the Calcaneus, Navicular, and First Metatarsal During the Stance Phase of Walking.

    I am obviously missing something obvious here and i could use some help with what!

    Graph B shows heel strike in inversion moving through to maximal eversion by heel lift. Which is about what i was expecting.

    Graph C shows tibial rotation. It appears that the tibia is most internally rotated shortly after heel strike and becomes more Externally rotated towards heel lift.

    Like i say, i'm missing something here! How come the tibial is externally rotating as the calc is everting (the foot pronating). Should'nt it be internally rotating as the leg loads?!

    This graph, nicked from craigs notes (thanks craig)


    Shows the foot to be at maximal pronation at HS becoming slightly more supinated by heel lift. Which fits with the tibia externally rotating through mid stance. But it also shows the foot to be maxiamally pronated at Forefoot loading. Which would seem to NOT fit with Graph B which shows the calc to be slightly inverted at this point.

    Thanks guys.

    Robert :sinking:

  2. Robert:

    This is a great question. Normally, we would expect, due to the triplane nature of the subtalar joint (STJ) that as the calcaneus everts the tibia should internally rotate and as the calcaneus inverts the tibia should externally rotate. However, you must also remember that each of the joints of the human foot and lower extremity have some "slop" in them or, to put this into biomechanics terminology, the movements of a number of joints in series might be considered to be "loosely coupled" like a loose spring rather than "tightly coupled" like a door hinge.

    In other words, in the example you provided above, even though the STJ may be everting during the midstance phase, the leg above actually may be externally rotating due to the external rotation of the pelvis and femur above the tibia. This indicates that calcaneal eversion-inversion is not tightly coupled to tibial internal-external rotation. Chris Nester did some research that showed that subjects had about 10 degrees of transverse plane motion available between the tibia and talus within the ankle mortise. The findings from the graphs you provided could be explained using these ideas.

    Remember also that McPoil and Cornwall used skin mounted markers which are known to have fairly significant differences relative to underlying bone motion. In addition, these graphs represent averages of motion of many subjects, not individual movement patterns for one subject. These research problems may also influence our interpretation of their results on the coupling nature of tranverse plane tibial rotation to frontal plane calcaneal rotation during human walking.

    There are no stupid questions in biomechanics.
    Last edited: Mar 26, 2008
  3. I agree with Kevin re: coupling between the talus and tibia. This reminds me of the "anomaly" in Saraffian's work on the STJ that Craig alluded to in "past, present, future..." Can't put my hand on it right now, but I seem to recall he also said that you get internal rotation of the shank with STJ supination and external rotation with pronation.

    To me, the more interesting observations stem from the calcaneal motions in the frontal versus sagittal planes observed in graphs A and B. What's happening here? What are the reference frames being used? What, if anything, does this tell us about windlass function?
    Last edited: Mar 26, 2008
  4. Thanks for that!

    You say that the leg may be externally rotating above the femur. I suppose something i failed to consider is that the pelvis will be rotating around the stance leg as the swing leg advances.

    I don't have the paper to hand (now at home) However a quick glance at Rose and Gamble, Human Walking (great book) shows the same sort of graph for femoral rotation. It also shows a graph for pelvic rotation.

    Pelvic rotation moves from about 7 degrees internal to 10 degrees external during mid stance. Femoral rotation moves from about 7 degrees internal to about 3 degrees external for the same period.

    Could it be reasonably argued that the femoral rotation is therefor comprised of the pelvic external rotation minus the internal rotation at the hip joint? Does that make any sense? The whole unit externally rotates but the femur externally rotates less than the pelvis because it is symultainiously internally rotating in the hip?


  5. This highlights the need to provide specific details of reference frames. The femur rotates x number of degrees relative to what? The pelvis? The floor? You may well be right in your assertions above Robert, but unless you know what the frames of reference were, you cannot be certain. That said, providing the same reference frame is used throughout your assumption seems sound enough. Problems arise in cross-comparison of papers where different references have been employed.
    Last edited: Mar 26, 2008
  6. Pedantic I know, but I was taught that in anatomy the leg was the portion of the lower limb below the knee. Anyway, the point I came back to make with this posting is what Kevin and I were saying is that the leg as defined above can be externally rotating even though the STJ is pronating. Moreover, the leg may be externally rotating even though the femur may be internally rotating = torque across knee (train wreck) usually = pain- ouch. In other words, you don't always have "close coupling" between any of the joints in the kinetic chain. But coupling will vary with the joint positions.

    Question: looking at the anatomy of the ankle joint, what positions of the ankle joint are likely to result in maximal and minimal coupling between the STJ and the leg?
  7. Craig Payne

    Craig Payne Moderator

    See this thread: Foot orthoses and rearfoot/tibia coupling patterns

    The only thing I can add is that there is substantial variability in this from person to person and the data presented in graphs is often just the mean.

    Mark Cornwall presented some of his and McPoils work at PFOLA last year (its not published yet). They used a multiple components analysis to look for different patterns of rearfoot motion -- they were able to identify 4 distinct patterns that almost all of the sbjects fitted into ---- this is a substantial improvement in the methodologies of just using the "mean" pattern.

    Robert -- as soon as its published, will post it here. It will throw some light in your question.
  8. Valid point, well made. I beleive the reference point used in rose and gamble was a z axis perpendicular to the floor (i'll check later). I did notice that the graphs were not referenced so i presume the same method was used for all the data (yes i know, prusumption is the mother of all **** ups).

    Worth bearing in mind though!

    Your point about the knee is also worth bearing in mind. I did include a space in my ever lengthening equation for degrees of transverse freedom through the knee but i've been treating that as zero to stop my brain melting. That was also one of the things i questioned in terms of proximal rotators (glutmax, piriformis etc) in controlling foot position. External rotation moments from above meet internal rotation moments from GRF across the STA coming the other way... Sounds like trouble to me!


    The weakest link?

    Thanks for the link Craig, i shall await the paper with avid interest!

    Thanks all

  9. Robert, Simon, Craig and Colleagues:

    Here are a couple more articles that may shed more light on the subject:

    Hope these abstracts and pdfs of the papers help.
    Last edited: Mar 27, 2008
  10. efuller

    efuller MVP

    So the question is why is the STJ not supinating as the externally rotates. Kevin pointed out the joint above talus. We should also look distal to the calcaneus. With midtarsal joint motion it is possible for the calcaneus to externally rotate without supinating/ inverting. That does make an interesting research question. How much does the calcaneus internally or externally rotate relative to the ground with a comparison to how much the leg rotates relative to the ground.

    As a student I remember watching someone walk while John Weed was commenting on gait. The walker was exhibiting late stance phase internal rotation and John Weed called it STJ subluxation. Later, when looking at anatomy, I was trying to correlate what I was seeing with actual motion of bones. I still don't see how it is possible to sublux the STJ in walking. When the STJ is maximally pronated the lateral process of the talus hits the floor of the sinus tarsi. It is not possible to pronate further without breaking bones. If you see late stance phae internal leg rotation The STJ is either not at the end of its range of its range of motion, or the motion is occuring at some other joint. I think what John Weed was calling subluxation was reafoot adduction on the forefoot. I think people still make the mistake of ignoring the midtarsal joint when thinking about foot motion.

    That said, Craig's point about averages is valid because not everyone has external leg rotation when the average graphs say they do. Some people have late stance phase internal leg rotation.


  11. Eric and Colleagues:

    The question seemed to be how could the calcaneus be everting while the tibia was externally rotating. Midtarsal joint motion of the calcaneus moving relative the cuboid/navicular should not matter since the motions of interest are the transverse rotations of the tibia relative to the ground and the frontal plane rotations of the calcaneus relative to the ground. Whether or not there is or isn't midtarsal joint motion won't necessarily affect calcaneus to tibia motion since the midtarsal joint is not between the calcaneus and tibia, it is distal to both. Of course, midtarsal joint motion may cause both the calcaneus and tibia to rotate within space, but won't necessarily affect the relative rotations/translations of the calcaneus and tibia to each other. Just wanted to clarify this for those following along.
  12. David Smith

    David Smith Well-Known Member


    Simon has probably hit the nail on the head in terms of reference frames.

    If one considers two bodies, one in orbit about the other, ie like a moon around the earth. Then a certain point on the surface of the moon may have a clockwise rotation about the moons centre (for arguments sake). The orbit about the earth may be anticlockwise. The same point on the moons surface now has an anticlockwise rotation in terms of the earth centre.

    Imagine now that a plan view of the hip, knee and ankle centres would reveal they are no congruent especially when the knee is bent and has a tendency to be medial to the hip and ankle. In this view the joints would tend to orbit each other.
    Perhaps the knee and ankle are congruent and the knee orbits the hip. You might see that if the tibia internally rotates thru a small arc at a low velocity but the hip joint rotates externally thru a greater arc at a relatively high velocity then the overall direction of a marker of interest on the knee may be external rotation in terms of the pelvis or some lab coordinate but the rotation of the same marker relative to the ankle coordinate could still be internal rotation.

    To avoid ambuguity it is required that a very robust definition and understanding of that definition is applied to the characterisation of joint and limb active RoM thru gait. If a local reference frame is used then it must be remembered that this reference frame changes relative to the global or lab reference frame as the displacement of the limb changes.

    Try this experiment. Sit with knee flexed at 90dgs. knees and feet point directly ahead and your feet longitudinally aligned with your femur. Now Externally rotate your right foot, by spining on the heel of your right foot, but do not move your right knee. If you are flexible you will externally rotate your foot 70 - 90dgs relative to your knee or you could say that your knee is now internally roted by 70 - 90dgs relative to your foot. Now externally rotate your hip by 45dgs without moving your foot. Now your knee and tibia are externally rotated relative to it's original global position but still iternally rotated relative to your foot. Did your tibia internally or externally rotate. It depends on your point of view. There is a similar action to this thru the gait cycle.

    Did I explain that clearly?:confused:

    Cheers Dave:drinks
  13. Crystal.

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