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When Does the Subtalar Joint Resupinate During Walking Gait?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Kevin Kirby, Apr 27, 2015.


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    I just got done with one of my Precision Intricast Newsletters where I detailed the bone-pin research on 8 subjects by Close, Inman, Poor and Todd from 1967 (Close JR, Inman VT, Poor PM, Todd FN: The function of the subtalar joint. Clinical Orthopedics, 50:159-179, 1967). [See their paper attached below.]

    What I find interesting from the bone-pin research of Close et al on 8 live subjects while barefoot walking, was that they did not have a single subject that had a subtalar joint (STJ) that started to supinate in early midstance or at the middle of midstance. Rather in all their subjects the STJ began to supinate at the time of heel off, which is what I have seen clinically in the vast majority asymptomatic feet over the past three decades during barefoot walking gait examinations.

    Here is a quote from the paper by Close et al: "Very early in stance, in most of the curves, there was brief internal rotation of the calcaneus on the talus. This was followed by a longer period of external rotation or pronation. This interval represents the period of maximum weight-bearing. As the metatarsophalangeal angle changes abruptly at each curve of each subject, the calcaneus simultaneously reverses its rotation from external [pronation] to internal [supination]. Thus, the stance phase may be divided into 3 periods regarding subtalar motion."

    This data from Close et al, as you may already know, is in direct conflict to what is taught in podiatry schools around the world that the foot supinates much earlier in gait. In fact, in Root, Orien and Weed's book published ten years later in 1977, Root et al make the following claim on page 137: "With onset of the midstance period, the leg begins to externally rotate, and closed chain supination occurs at the subtalar joint." (Root ML, Orien WP, Weed JH: Normal and Abnormal Function of the Foot. Clinical Biomechanics Corp., Los Angeles, CA, 1977). See the "gait graph" from page 145 of Normal and Abnormal Function of the Foot illustrated below.

    When I looked at what reference Root et al used to justify their claim that the STJ supinates at the beginning of midstance, just after the time of forefoot loading, they used the 1964 paper by Wright, Desai and Henderson which used just three subjects and measured STJ motion, not with bone-pins, but rather with an external cast-shoe-hinge apparatus that indirectly measured what was thought to be STJ range of motion through the soft tissues of the leg and foot (Wright DG, Desai SM, Henderson WH: Action of the subtalar and ankle-joint complex during the stance phase of walking. JBJS, 46 (A): 361, 1964). For all we know, Wright et al could have been measuring ankle joint motion, not STJ motion, with their apparatus. They also referenced a book chapter by Eberhart, Inman and Bresler from 1968 as a reference which I don't have access to.

    Certainly Root et al must have been more research evidence than just one or two papers using three subjects to claim that the STJ starts to supinate "at the onset of midstance phase" of walking gait??? I believe it would have been better, at the time of publication of their book, for Root et al to claim that the STJ doesn't supinate until the end of midstance by referencing the much better bone-pin study by Close et al done in 1967.

    What does everyone else think?? Anyone have any ideas???
     

  2. Jarvis suggested that peak eversion occurs around midstance. http://usir.salford.ac.uk/29381/1/HannahJarvis_PhDThesis.pdf
     
  3. Phil Wells

    Phil Wells Active Member

    Kevin

    This may be a silly question but is the bone pin method of study limited in that it can only show actual bone movement and does not reflect what is happening with the moments in the foot? What I am getting at is that the foot may be building 'tension' in soft tissues in the direction of supination much earlier than Inmans' study indicates and it may be incorrect to assume timing's using this method.

    Cheers

    Phil
     
  4. Another point

    does it really matte?r, sure it might be a hole in the work of Root, but if and when the foot re-supinates is it that important?, the main question is are they pathological or not , if not then when an individual re-supinates or not does not really matter.

    Sure this might be part of the 1000 Norms project and interesting to a point.....

    I for one wish they would not use Normal anywhere in the text, but discuss likelihood of pathology or injury development
     
  5. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    I away from main computer to look up, but I do recall a study (maybe Cornwall/McPoil) with a lot of subjects looking at this. They collected data and then did a principal components analysis and found 3 or 4 distinct patterns ... ie there was no "normal" but 3 or 4 different patterns.
     
  6. Dananberg

    Dananberg Active Member

    Hi Kevin,

    Interesting topic. My thinking on this involves what promotes Supination in the STJ. There are essentially two components. The first is external rotation of the limb brought about by opposite limb swing phase, and the 2nd is the windless. The swing limb must pass beyond the frontal plane of the stance limb for this to even begin. Then, as the Supination moment is being imparted from above (proximal to distal), the windless acts in a distal to proximal fashions, so both can coordinate to supinate the foot and externally rotate the limb. Hicks showed how the effect of the windless can be seen as far as the proximal femur. This would explain the Close findings.

    In pressure analysis, this correlates with the timing of the terminal phase of calcaneal unweighting just prior to heel off. When the windless is inactive, ie, Functional hallux limitus, the distal to proximal supinatory impetus is lost. This is why, IMHO, that we see pathologic Pronation so late in the stance phase.

    Why Functional hallux limitus occurs is for another discussion. But without metatarsal base rotation about the heads, the distal to proximal counter to the force of gravity cannot be overcome.

    Muscles play a fairly limited role in this entire process. This is an interesting component to the discussion if anyone is interested.

    Howard
     
  7. Phil:

    Bone pin studies are the gold standard for determining the kinematics of gait. As such, they actually tell us what is truly happening at a joint and especially a joint such as the subtalar joint (STJ) where it is extremely difficult to know exactly what a "hidden bone", such as the talus, is doing at any time during gait without having a bone pin drilled into it.

    Moments are another matter and represent the field of study of kinetics. However, in a clinical setting, doing gait examinations or video analysis of patients is only measuring the motion patterns (i.e. kinematics) of the foot and lower extremity. The moments acting across the joint axes at any instant in gait is much more difficult to ascertain and is basically educated guesswork, unless one has a 3D motion analysis system, a force plate and inverse dynamics software to get a better handle on the kinetics of the STJ and other foot and lower extremity joints.
     
  8. Mike:

    Yes it does matter when the foot resupinates. Why? Because when a foot resupinates is an indication that the STJ supination moments are greater than the STJ pronation moments at that instant in gait and also that the transverse plane rotations of the tibia, femur and pelvis are matching the rotations of the foot during walking gait. I believe this is something that is critically important in improving gait efficiency.

    In other words, Mike, do you do gait analysis on your patients pre- and post-foot orthosis application? What types of objective analysis do you do to determine whether the foot orthosis is improving the gait of the patient? Do you look at STJ supination and when it occurs, or if it occurs? Or do you just give the patient their orthotic and not evaluate their gait function, simply hoping that it will help them with their pain, but not doing any objective measure of how the orthosis improves their gait function or not? What if a patient never resupinates during gait with your orthosis, do you consider this to be beneficial for your patient?
     
  9. Jeff Root

    Jeff Root Well-Known Member

    Cornwall and McPoil used tibial rotation as an indicator of STJ motion in this study:

     
  10. Jeff Root

    Jeff Root Well-Known Member

    http://fai.sagepub.com/content/20/8/513.short

     
  11. depends on what pathology I am treating.

    Every thing I do depends on what the complaint is and what I determine the best way to treat them. If a patient comes to me and I believe earlier or later re supination than they currently indicate to me during their biomechanical will benefit then I design and construct their device, to try and achieve that.

    not all patients are the same and therefore designing foot devices to achieve the same timing of re supination I believe not the best way forward in thinking.

    otherwise we may as well construct another list of " normal"
     
  12. One of the questions that comes to my mind, is when does the STJ begin to resupinate when we are not walking barefoot across a flat, horizontal lab floor? In other words, to what extent does the "real world" environment impact on this?

    Which kind of leads to my next question: why does the segmental coupling vary between and within individuals? What might the evolutionary advantages of this decoupling be when we are not just walking up and down in a biomechanics lab?
     
  13. I believe that STJ resupination occurs much earlier in midstance in feet walking in heeled shoes (Wright, Desai and Henderson) versus walking barefoot (Close et al). Therefore, it's critical to understand that when comparing studies or making statements about what "normal" resupination is, that what is "normal" for barefoot walking may not be "normal" when wearing heeled shoes. The extra heel height probably either decreases the Achilles tendon tension and/or preloads the plantar fascia...either of which may cause the earlier resupination in most individuals when wearing heeled shoes.
     
  14. If Achilles tension is reduced shouldn't resupination occur later given that the gastoc-soleus (GS) unit via the Achilles is a supinator in most? Which begs the question: what drives the resupination? Is it directly muscular, i.e. Achilles tension from GS contraction; and/ or is it, tibio-talar coupling with the tibia being driven from proximal to distal? Which leads inevitably to: what effect does GS contraction have on tibio-talar coupling?
     
  15. Phil Wells

    Phil Wells Active Member

    Thanks Kevin

    However I do understand this is the Gold standard at the moment but it tells us nothing of the underlying forces that the bone study is seeing. To use your 'own' rotational equilibrium of the Stjt and Eric's description of CoP relative to this axis, the foot is actually dynamic and may actually be re-supinating far earlier in gait but the 'tipping' point to create a Kinematic result is only seen much later.
    As you say these moments effects on the Kinetics are very difficult to measure but that does not mitigate the fact that they are present.
    Lets not assume that the foot is doing one thing based on something that has it own limitations.

    cheers

    Phil
     
  16. Jarvis actually showed that the feet pronated throughout midstance until just before heel-off.

    What Jarvis found is exactly what was seen in the bone-pin study by Close et al in 1967: the STJ pronates throughout midstance until just before heel off when it starts to rapidly supinate (see chart below from 217 of her thesis).

    The question then remains...where did Root et al get the data to construct the graph that I showed in the first posting? The graph from Root et al certainly doesn't resemble any of the bone-pin graphs from Close et al from 1967. If anything, the graph from Root et al looks more like the data from Wright et al. Maybe Root et al's graph represented what they thought represented an "ideal" foot, and didn't base their graph on previous research? It's a mystery to me.
     
  17. I flipped through Jarvis's PhD thesis again this morning and was going on this statement at the bottom of p.258 "the maximum everted position of the subtalar joint during the stance phase of walking is not at forefoot loading. Instead, the peak angle of eversion occurred during midstance. " I think we need to differentiate between pronated but supinating, and supinated and supinating. To me, resupination begins when the STJ is supinating whether it is in a pronated position at this time or not. In which case the left foot starts to resupinate at about 32% in the graphs above; toe off occurs at about 64%, therefore resupination begins at about midstance. It was later in the right foot data.
     
  18. Phil:

    I believe you are getting motion (i.e. kinematics) mixed up with moments (i.e. kinetics).

    The bone-pin studies are only looking at bone motions or kinematics. From these motion patterns of the bones, one may then infer that certain moments may or may not be present. In other words if the STJ shows an acceleration of supination motion in a bone-pin study, one may infer that either the STJ supination moments increased and/or the STJ pronation moments decreased to cause a net increase in STJ supination moment. However, if no change in STJ motion is occurring, then one can assume that the STJ is in rotational equilibrium with an exact counterbalancing of STJ moments at that instant of gait.

    Therefore when you said "..the foot is actually dynamic and may actually be re-supinating far earlier in gait but the 'tipping' point to create a Kinematic result is only seen much later." What you should have said is "the foot may have a STJ supination moment occurring within it far earlier in gait but there may have been another source of STJ pronation moment occurring at the same time that prevented it from undergoing supination acceleration."

    Of course moments are present in every situation within the human foot, but if these moments are exactly counterbalanced, there will be no foot movement occurring. A lack of motion does not imply a lack of moments which is a principle I have been teaching and writing about now for over a quarter century (Kirby KA: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989).

    However, when I see a foot starting to resupinate not until heel-off versus starting to resupinate in early midstance, I can guarantee you that the balance of STJ supination moments vs STJ pronation moments is greater in early midstance in the foot that starts to resupinate in early midstance than in the foot that pronates throughout the midstance phase of gait.
     
  19. Agreed.

    Supination is a motion, regardless of whether the foot starts more pronated and ends less pronated, or the foot starts pronated and becomes supinated, or even if the foot starts less supinated and becomes more supinated.

    Also, the graphs on Jarvis's PhD thesis indicates maximum calcaneal eversion occurring about at the 3/4 point of midstance, just before heel off, from my best estimate.
     
  20. Agree
     
  21. Jeff Root

    Jeff Root Well-Known Member

    Kevin,

    See Subtalar Joint Motion (stance phase) on pages 135-139 of Normal and Abnormal Function of the Foot. There are several references listed for the motion of the various joints and segments during stance phase STJ motion including Close and Inman, Wright, Whitney and others. It appears that they compiled their data (graph) from multiple sources.

    Jeff
     
  22. Repectfully, I disagree.
     
  23. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    This was the study:

    Classification of Frontal Plane Rearfoot Motion Patterns During the Stance Phase of Walking
    Mark W. Cornwall, PT, PhD, CPed and Thomas G. McPoil, PT, PhD, ATC
    J Am Podiatr Med Assoc 99(5): 399–405, 2009
     
  24. Where do you think maximum calcaneal eversion occurs on Jarvis's graphs, Simon?
     
  25. Here is the graph of the four "foot types" from Cornwall and McPoil's study.

    And the last paragraph from their paper:

    Basically, then, Cornwall and McPoil also showed that 94% of the subjects didn't resupinate until just before heel off, which generally occurs at about 70% of stance phase.
     
  26. drhunt1

    drhunt1 Well-Known Member

    A hole in Root's work? Please....

    Pay attention, because IMHO, this is where the "rubber meets the road" not only for our profession, but many pathologies that walk, (or limp) into our offices and those of orthos.
     
  27. drhunt1

    drhunt1 Well-Known Member

    I want to thank Kevin for this topic...but I have a question...what took you so long to discuss this?

    On page 137, (Root et al clinical Biomechanics, Vol. 2, paperback), they write:

    "A normal foot does not pronate beyond the contact period. When observing gait, the normal rearfoot reaches its maximum position of pronation at the end of the contact period, which corresponds with toe off of the opposite foot." While the description is a little muddled, (at least in my mind), after that, this is where we, as a profession, can and should expand on that groundwork. Many pathologies occur in the LE due to the patient NOT supinating when they're supposed to...something I'm now working on. Further, I believe that ultimately, this is one of the major reasons we witness HAV and bunion deformities...as well as many other painful conditions. Root just gave us the outline...we should be filling in the text.
     
  28. The left foot starts to resupinate at about 32% in the graphs above; toe off occurs at about 64%, therefore resupination begins at about midstance. It was later in the right foot data with resupnation at about 38%. The right foot data seems to support your conjecture, but I don't think the left does. It would have been helpful to have seen the confidence intervals displayed graphically with this data.
     
  29. My calculations from looking at the graph are that the left foot starts to resupinate at about 69% of midstance phase and the right foot starts to resupinate at about 82% of midstance phase meaning that the two feet started to resupinate, on average, at 75% of midstance phase.
     
  30. Dananberg

    Dananberg Active Member

    Kevin commented. "The extra heel height probably either decreases the Achilles tendon tension and/or preloads the plantar fascia...either of which may cause the earlier resupination in most individuals when wearing heeled shoes."

    Increased heel height causes the MTP joints to dorsiflex far sooner than barefoot. Reupination is likely related to this phenomena.

    Howard
     
  31. efuller

    efuller MVP


    Is there a reason for having a "normal" point in gait for when resupination should occur. When I had access to an EMED force platform, when I looked at several different steps, I remember quite a bit of variability across steps. Dynamic gait is a constant rebalancing process. (Made very obvious after a few drinks). In light of this not every step should be the same. Even in walking a straight line, there are minimal errors of foot placement that need to be corrected for in the next step. One mechanism to achieve correction in balance is to shift the center of pressure under the foot with a little more posterior tibial or peroneal muscle activity that will also tend to change the STJ position.

    The McPoil article that showed different strategies makes a lot of sense. Not every foot is the same. So, it makes sense that different feet choose different strategies. We certainly should establish some criteria if we are going to say one strategy is more "normal" than another. What criteria did Root etal choose when deciding what should be normal?

    Achilles tendon tension and heel lifts/ shoes. There was a study done by Nigg that found there was not a reduction in tension with a heel lift. For one reason there is going to be active contraction of the gastroc and soleus muscle to provide propulsion or at least prevention of the talus banging into the anterior aspect of the tibia.

    Eric
     
  32. Eric:

    I think the clinician should be aware of what "ideal" is and what the "normal variants from ideal" are when assessing gait. Cornwall and McPoil's article is a good starting point. Yes "ideal" is theoretical, but it certainly gives us a starting point by which to see how much variation from this ideal can still produce functional gait patterns which are asymptomatic.

    I do worry about just looking at asymptomatic individuals and then considering that these feet should then be considered "normal", just for the sole criteria that they are asymptomatic. I think we can do much better than that given our current level of understanding of foot and lower extremity biomechanics and foot and lower extremity structure.

    However, I also don't like many of Root et al's Eight Biophysical Criteria for Normalcy since these rely on taking measurements that are not reproducible. Maybe it is time to come up with a set of "Biophysical Criteria for Optimum Foot and Lower Extremity Structure and Function" to amend/replace Root et al's "Biophysical Criteria for Normalcy".

    Anyone care to stick their neck out on that one?:drinks
     
  33. Jeff Root

    Jeff Root Well-Known Member

    Eric, don't you know that you shouldn't be drinking while you're evaluating your patient's gait, even if it does make things more obvious to you! ;):drinks
     
  34. efuller

    efuller MVP

    Drinking only while evaluating gait at biomechanics conferences. Sorry, I missed Vancouver.:drinks
     
  35. efuller

    efuller MVP

    Instead of looking for "normal" we should be looking for observations that are likely to lead to pathology that we can fix/prevent. For example, the extremes of STJ axis position. I think I can make the case that a STJ axis that is two standard deviations from the mean should be treated. When you look at a sock liner of a shoe and see a really deep impression under the hallux, then we might be able to predict that this person is likely to have pathology later, whether or not they are having symptoms at present. I think we can make an orthotic that will prevent/delay pathology in that foot.

    What is the purpose of defining a normal gait? Do we want to make everyone walk normally? Will people with a normal gait still get foot pathology? Will all people who do not have a normal gait get pathology? What criteria do we use to select what a normal gait should be?

    Eric

    Eric
     
  36. Petcu Daniel

    Petcu Daniel Active Member

    Could somebody help me with a copy of the article mentioned in this thread:
    Classification of Frontal Plane Rearfoot Motion Patterns During the Stance Phase of Walking, Mark W. Cornwall, PT, PhD, CPed and Thomas G. McPoil, PT, PhD, ATC
    J Am Podiatr Med Assoc 99(5): 399–405, 2009 ?

    Thanks in advance,
    Daniel
     
  37. Petcu Daniel

    Petcu Daniel Active Member

    In the Close's study we have the gaph of Ɵ angle which, in my understanding, is measured in the transverse plane and is representing the movement of the calcaneus relative to the talus. Also, the heel off I suppose we can find based on the ankle motion graph [probably the point where the angle is between 80-90 degrees]. In the graphs from Javris thesis we have the graph of the motion of the calcaneus relative to the tibia in the frontal plane. Could we compare these graphs ?
    Sincerely,
    Daniel
     
  38. What is the purpose of defining a normal gait? So we can determine when the gait is normal or abnormal or not, that is why.

    Do we want to make everyone walk normally? No that is an impossibility since not every one has the capability to function normally. However, the ethical clinician can certainly prescribe measures that will improve the function of the patient's gait. In addition, if one has good knowledge of gait examination techniques, then one can diagnose conditions that may very difficult to detect by using other screening measures.

    Why even watch someone walk with or without an orthosis if we don't think that the kinematic patterns within the joints of the foot and lower extremity during gait are important either as an indication of pathology or lack of pathology?

    Analyzing gait doesn't have to be just for determining whether an individual will develop pathology any more than doing a blood test today determines whether a patient will, a year later, develop leukemia or anemia. Rather, gait analysis is used to determine the integrative functioning of the central nervous system, peripheral nervous system, musculoskeletal system and function of the foot and lower extremity during walking or running gait at that instant in time.

    And as far as asking what criteria we should use to determine normal gait function, this has been discussed in great detail within the literature by individuals such as Verne Inman and Jacquelin Perry for decades. I would think this sort of question need not even be asked.

    In addition, I have been teaching gait examination techniques for the last three decades at national and international biomechanics seminars. I consider the skill of determining normal and abnormal gait patterns to be as important, if not more important, than any other examination technique that a clinician can assess for a patient. Why? Because the gait examination is the only method by which we can determine the proper functioning of the central nervous system with the musculoskeletal system of the bipedal human during locomotor activities.
     
  39. But "normal gait" is unique to the individual at an instant in time in a given environment for given locomotor task. There is no one all defining "normal gait".

    Do I need to say it again? The phenotype "normal gait" (P) is a function of the genotype (G) + all the non-genetic factors, otherwise known as environment (E) + the interaction between genotype and the environment (G + E), then there will be some measurement error (i)

    So we have: P= G+E + (GxE) + i

    There is no single "normal gait", end of story. What shade of skin is normal?
     
  40. Eric:

    Just using STJ axis location, by itself, is a blunt tool to predict pathology. I see many patients with medially deviated STJ axes function relatively normally since they have good muscle strength that overcomes the non-ideal STJ axis position. I see many patients with what appears to be abnormal insole wear patterns that function fairly normally and are asymptomatic.

    Therefore, I can't agree with you that we can use STJ axis location or shoe insole impressions, by themselves, to predict pathology, any more than we can use the measurements advocated by Root et al, by themselves, to predict pathology, due to the numerous other parameters which affect the function and production of pathology within the human locomotor apparatus.

    Rather, we need to use all evaluation techniques that we have available to us, including STJ axis location and shoe insole impression, to learn more about our patient's foot and lower extremity function so that we can better improve their lives. The human body is too complex and too variable to start limiting ourselves in our evaluation techniques of our patients....we have only started to scratch the surface of our knowledge of the complexity and variability of the human foot and lower extremity
     
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