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Variability and Foot Biomechanics

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Ian Linane, Aug 20, 2005.

  1. Ian Linane

    Ian Linane Well-Known Member

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    <ADMIN NOTE: This thread on variability has been split off from the thread on Measuring LLD as its worthy of its own topic>


    Kevin, you suggest:

    "it is very painful for many podiatrists who are currently "comfortable" with their version of reality to change their "belief system"."

    True in so many circles. And very true when it comes to changing our belief systems.

    But could this be applied in the same way when it comes to accepting that the natural position of the foot is Varus with a moderate amount of forefoot varus as well? Especially as it seems to challenge the comfort of so much of how podiatric biomechanics is written about in our text books.

    Last edited by a moderator: Aug 22, 2005
  2. Do we have a study that shows that the "natural position of the foot is varus with a moderate amount of forefoot varus", Ian?? I have seen many feet with a forefoot varus and seen many more feet with a forefoot valgus during clinical exam (using the Root measurement system). In addition, I have seen plenty of feet with an inverted rearfoot and many with an everted rearfoot in relaxed bipedal stance so, in this case Ian, what then would be considered the "natural position" in this wide variety of feet?

    After examining thousands upon thousands of feet over 20 years of practice and teaching biomechanics to podiatry students and podiatrists in many countries, I have come to the conclusion that the human foot is highly variable and that there is no natural position of the foot. I would agree that the varus rearfoot is much more common, as long as you are using the subtalar joint neutral position as your reference. However, when one uses a position that is pronated from the STJ neutral position, then varus is much less common and, in fact, the valgus position then becomes more common. This then leads to the basic question of: Do we really know that the STJ neutral position is the ideal position of function when nearly all the population functions pronated from the neutral position?? This idea that STJ neutral position if the ideal position of STJ function in all individuals is another commonly accepted idea held by podiatrists but we really have no scientific basis by which to form this opinion.

    I think that you will see, Ian, that in the two books that I have published, that I speak very little on the STJ neutral position when discussing the kinetics of the foot and lower extremity since I am much more concerned with STJ axis spatial location. Many feet that stand in their STJ neutral position are in an unstable position and are much more stable in the STJ pronated position. So how then, Ian, do you know that the "natural position of the foot is varus with a moderate amount of forefoot varus as well"??
  3. Ian Linane

    Ian Linane Well-Known Member

    Hi Kevin

    Thank you for the honest reply. I understand your comments.

    I would certainly agree that the human foot is naturally infinitely varied (isn't this one of the significant bits of information missing from so much of the biomechanics literature) but would also suggest that my own experience is that the foot, in STJ neutral, invariably sits comfortably in a rear foot varus position (albeit with some exceptions). I am aware that David H has done some studies along the lines. When I then apply how I was trained to assess the forefoot at this point (Langers a long time ago, and I am happy to shift my belief on this approach)) I commonly see a supinatus forefoot position, frequently accompanied by a plantar flexed 1st ray. Certainly I have not seen it in a rectus position.

    It is for a number of the reasons that you mention above that I have long since moved away from using incremental foot measurements ( my approach which I acknowlege does not hold favour with yourself). When presented with a foot that has to walk on a uniformly hard and flat surface I now consider it to be simply a determing the question of balance, not of foot type. How can I help that person balance in movement and stance in a way that is most efficient?

    Whatever a persons foot shape (as opposed to type) it is normal and natural to them.

  4. I don't think that the approach that you use in your patients, Ian, is that much different than the one I use. Changing away from STJ neutral to another frame of reference is, indeed, a major change for a podiatrist treating mechanical problems of the foot. I am not so concerned with pushing harder and harder on the patient's foot until they attain the STJ neutral position, since this may cause problems in many feet. I strive toward three goals when I treat patients with foot orthoses:

    1. Reduce the pathological forces on the injured structural components of the foot and lower extremity to allow more rapid healing to occur.
    2. Optimize gait function.
    3. Prevent new injuries or pathologies from occurring.

    Now, in regards to your insistence that it is the hard, flat ground along with a varus foot that causes so much pathology, have you ever considered if you didn't use the STJ neutral position that you use (i.e. pronate the foot a couple of degrees from your STJ neutral position) and then drew your heel bisection line on a few more degrees everted, that you would find that there were a whole lot of feet now with much less rearfoot varus?

    In other words, how you "measure" the foot....you use your STJ neutral position as a reference....will greatly affect how much varus you see in the forefoot and rearfoot. Therefore, if we were to consider that, for example, the position of the foot that is 3 degrees from maximally pronated is the ideal rotational position of the STJ for the human foot to function in (instead of what you consider to be STJ neutral position), then I think you would find much less varus in the feet you examine and possibly not have come to the conclusion that accommodation of varus feet to flat surfaces is the cause of the vast majority of foot pathologies.
  5. Craig Payne

    Craig Payne Moderator

    Variability is big, but I disagree with it missing from the literature (maybe the podiatric biomechanics literature), but variability is a hot topic in the biomechanics world at the moment and literature and at the recent ISB it kept coming up all the time.

    Here are some eg's I use:
    1. We published some data a few years ago on how foot orthoses and heel wedges changed frontal plane calc angle, on average - BUT look closer at the data and some people actually evert more when standing on a medial heel wedge or inverted orthoses.....don't figure :confused:

    2. In one of Beno Niggs projects I extracted a table I use in a powerpoint in which he clearly shows that using a medial wedge, that some peoples knee abductor moment went up and in some it went down (given that a higher knee abductor moment is a major risk factor for knee OA, do we really have any idea what our foot orthoses are doing at the knee?.)

    3. As part of a grant application we developed an EMG methodology to include in the grant as a pilot. Changes in EMG repsonses of VMO and VL were measured in response to a very inverted foot orthoses. The mean of the five subjects was an earlier onset of VMO in response to the foot orthoses (this is a good thing for PFFS), BUT if you look closer at the data only 2 had earlier VMO onset and 2 had later onset and one did not change - but the overal mean was on earlier onset - do we really know what our foot orthoses are doing to knee muscle function?

    4. The list goes on ...

    I used to know what I was doing :eek:
  6. Ian Linane

    Ian Linane Well-Known Member

    Hi Craig

    One thing Kevin mentioned was how there are regional difference in the current levels of information. I suspect this applies here as well.

    In the Uk, although people have done biomechanics at college there can still remain a considerable amount of confusion for some. When you further attend courses run by companies the information does not usually refer to the high degrees of variability. Usually it is much more loaded to the rectus foot type and posted heels on the orthosis.

    This is what I implied by the biomechanics literature.

    I am unaware if Valmassey in his book addresses this significant area of variability.

    In many cases it is this type of company training that has fed biomechanical knowlege to people who did not do biomechanics at their training.

    It is, in part, because of the issue of variability that I have found that the simpler I can make it the better.
    Secondly, in our attempt to achieve the holy grail of orthoses are we being too reductionist in our approach possibly trying to grasp the minutia that may ( I emphasise may) complicate rather than help when it actually comes to a prescription.
    But there speaks a none researcher.
  7. Philip Clayton

    Philip Clayton Active Member

    STJ measurement

    Hello everyone I am new to the 'Arena' and thought I 'd better reply to my old friend Ian.
    Having taught students from all corners of the world in biomechanics I am of the conclusion that it is impossible to get ten students/experts to measure the same feet for stj/mtj/ncsp etc to within any degree of exactness that can be replicated. Often the more academic the student the less able they are to hold the foot and instruments and vice versa. Also most of the tractographs etc are poorly constructed. Like Kevin mentioned in his reply to Ian it depends on where you take your measurements from and also maybe to how you are taught and what preconceptions are bread into you from your tutor/college/text book.
    My first premise when teaching has always been to let the student make a good basic diagnosis before measuring anything and then to begin eliminating any basic mistakes i.e. is the forefoot in a varus or valgus position? Is it a forefoot varus or a forefoot supinatus? If supinatus this probably indicates an excessive pronation? Is this caused by an ankle equinus etc Then and only then would I move on to any form of measurements.
    I would then attempt to work through the maths to see if the numerical data confirms my initial diagnosis more like a detective eliminating all the false alibis.
    Sorry I've begun to ramble so I' ll wait for my first response!
  8. Craig Payne

    Craig Payne Moderator

    Philip - Welcome! :)

    We don't get the students to measure anything.
  9. Philip Clayton

    Philip Clayton Active Member

    I haven't measured anything for quite some time in my own practise but when I was teaching I had a fairly strict syllabus to follow. I still believe many experts are unable to find STJ or estimate ankle dorsiflexion and believe we should strive for much more relevant criteria based on successful patient compliance. Many of my patients are overweight, inactive, wear ill fitting shoes and very few labs make devices that will fit into the inappropriate shoes that they wear so the direction of the solution is more important than the level of degree of accuracy. A recent pro footballer came in requesting replacement orthoses, his other ones had been ruined in his washing machine, and I think he would have worn two accrington bricks in his boots if his previous specialist had asked.
  10. Craig Payne

    Craig Payne Moderator

    ...and even if they can, what does it mean.... I am about to get a powerpoint ready for next week's APodC conference on one of my students' work on ankle joint ROM:
    * no correlation between static range of motion and what people used dynamically
    * even if some had ten degrees, many of them never actually used it when walking slow and walking fast
    * some subjects never went past 0 degrees, even if they had more
    * when some walked faster, the needed a greater range of motion than 10 degrees ---- others just lifted the heel off the ground earlier (and never neede close to 10 degrees), even if the had >10 degrees available...
    * the range of motion measured is dependant on the force applied (see the thread on precise naming and "stiffness" and comments I made there)

  11. Ian Linane

    Ian Linane Well-Known Member


    David H and myself have observed the following and sometimes demonstrate it at the workshops we provide - especially if people get concerned about "ankle equinus":

    1. Pt prone, knee flexed to 90deg the practitioner places the foot in STJ neutral (important to keep the thing in tight to neutral), passively tries to get 10degs dorsiflexion. Invariably we can't. Last time we did this in a room of 14 people all 14 failed to get the 10degs.

    2. Move the foot out of STJ neutral even the minutest amount and you can get increased dorsiflexion, sometimes significant amounts.

    Some of the questions that have arisen for me over the years include:

    Is it possible that the concept of a condition called ankle equinus is erroneus if it is based around the traditional STJ neutral?

    Is it possible that moments of "equinus" are not equinus but an essential, momentary structural buttress to the low limb on certain terrains but not others?

    Is there a significant role/link between the foots capacity for the above and the various neutral moments ( sorry to murder biomechanical terminology here but I hope you get my drift) that may occur across the STJ?

    Does this make any sense?


    (Not sure who owes who a pint here Phil)
  12. Philip Clayton

    Philip Clayton Active Member


    The standard test for ankle equinus is with leg extended and patient dorsiflexing foot whilst keeping foot in STJ?

    More movement is available because the foot moves out of STJ neutral and hence 'unlocks'. It begins compensating which starts the chain of reactions in the gait and may lead to the development of symptoms.

    The operator pushing depends on their own relative strength not the patients ability to move the foot.

    Finding STJ neutral is the key most text books are unclear in advice. I tend to believe it is best found without looking, by feel. Using the art? Imagine a curve moving from inversion to eversion with the foot fully dorsiflexed. At one point on that curve there is a 'flattened' section where there is neither inversion or eversion ( a plateau ), which if you examine without looking at the movement, then a subtle but distinct area is found. No balancing curvature around malleolus or pushing fingers into ankle crevices just a repeatable and definable point of neutrality. Does this make sense?

    :cool: Philip
  13. dawesy

    dawesy Member

    It is important to note when we are talking about testing ROM at the ankle joint and its relevance to gait that it is a TRIPLANAR joint, hence accurate measurement with the foot in 'neutral' (whatever that is :) ) is probably imposible, if we move it in the sagittal plane to test whether 10 degrees is present, it also MUST move in the other two anatomical planes simultaneously.

    I found craigs research on discrepancies in static and dynamic interesting.... is 10 degrees important? I also check this measurement, although am aware how innaccurate we are at measuing a triplanar joint in one plane, and a lot of patients do respond well to vigourous calf stretches as an adjunct to therapy. Need more research as to what is going on, and an accurate measurement........
  14. The next time you and David H do this demonstration you should probably use a force that is close to equivalent to the subject's body weight. If you did your "test" with manual force (which seems to be the case from your description) I would estimate that you are at probably 1/10th the amount of force that the foot is subjected to at the time of heel off when the Achilles tendon loads are greatest. When you do this test using physiologic loads on the Achilles tendon, I would not be surprised that at least 75% of your subjects would easily get to 10 degrees of dorsiflexion.

    Also, STJ rotational position greatly affects this position as you note below. And since we can't all agree where STJ neutral position is, then holding the foot at a point that is 2 degrees more pronated than where you think neutral is may be the point within the STJ rotational positoin that another podiatrist may think is STJ neutral position.

    This is because as the STJ pronates, the calcaneus, cuboid and lateral metatarsals all dorsiflex relative to the calcaneus since dorsiflexion of the calcaneus, cuboid and lateral metatarsals relative to the talus is one of the cardinal body plane motions inherent to STJ pronation. What is even more interesting, Ian, if you desire to explore these relationships further, is that pronating a foot with a medially deviated STJ axis from a point which is 4 degrees from maximally pronated to the maximally pronated position will produce greater dorsiflexion of the foot relative to the tibia than pronating a foot with a laterally deviated STJ axis from a point which is 4 degrees from maximally pronated to the maximally pronated position. Do you know why this occurs? You may want to reread the last section of my paper on STJ axis location to help with the answer (Kirby, KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987).

    The condition of ankle equinus is not erroneus. However, the measurement of ankle joint equinus could be considered to be highly variable based on a number of factors which may occur with clinical examination of ankle joint dorsiflexion:

    1. Rotational position of STJ
    2. Magnitude of manual force from examiner on forefoot
    3. Location of center of pressure from examiner's hand relative to ankle joint axis (i.e. length of ankle joint moment arm)
    4. Line of action of manual force from examiner relative to ankle joint axis (i.e. vector spatial alignment)
    4. Magnitude of ankle joint dorsiflexion moment generated by patient's muscles during examination

    In the future, once we get over the pain of my suggestion to change our clinical terminology of first ray hypermobility to decreased first ray dorsiflexion stiffness, we will next begin talking about increased ankle joint plantarflexion stiffness rather than ankle equinus. I believe Craig has done some preliminary studies on this factor as well as other researchers, especially in regard to ankle joint stiffness in running and jumping activities. Change in age-old terminology is painful, but necessary to keep up with the rapid growth in knowledge in biomechanics.

    Ankle joint plantarflexion stiffness will be affected not only by passive plantarflexion moments such as Achilles tendon-gastrocsoleus muscle unit passive tension and posterior ankle joint capsular tensile force but also by active plantarflexion moments such as muscle contractile activity from the gastroc-soleus, deep flexors, and peroneals. The individual will modulate the ankle joint plantarflexion stiffness by modifying the magnitude and temporal patterns of the ankle jont plantarflexion moments that are controlled by the central nervous system. Differences in terrain, walking speed and other factors, such as central nervous system stimulation will cause differences in ankle joint plantarflexion moments and plantarflexion stiffnesses. The concept of ankle joint stiffness and rotational equilibrium across the ankle joint is critical to understanding the mechanics of the ankle joint during weightbearing activities.

    You have only badly wounded biomechanical terminology here, Ian. ;)

    The question you ask above is a subject near and dear to my heart and one day I hope to sit down and write a paper on this subject. To understand the mechanical interrelationships between ankle joint, STJ and MTJ, one must also understand the concept of simultaneous rotational equilbrium across the joint axes. In other words, if I apply a force on the plantar aspect of the 2nd metatarsal head, what simultaneous ankle, STJ and MTJ moments will occur? Next question, if the STJ is medial or laterally deviated, how will these change the STJ moments for the same applied 2nd metatarsal force? The answers to these questions may explain the results from Craig Payne's STJ tipover research that he was doing a few years ago.

    Maybe Craig can chime in here about that subject.
  15. davidh

    davidh Podiatry Arena Veteran

    Hello Kevin,

    You wrote
    "The next time you and David H do this demonstration you should probably use a force that is close to equivalent to the subject's body weight. If you did your "test" with manual force (which seems to be the case from your description) I would estimate that you are at probably 1/10th the amount of force that the foot is subjected to at the time of heel off when the Achilles tendon loads are greatest. When you do this test using physiologic loads on the Achilles tendon, I would not be surprised that at least 75% of your subjects would easily get to 10 degrees of dorsiflexion."

    I'm interested in how this measurement can be done clinically using a physiologic load which approximates subject bodyweight.

    I'm also interested in your opinion of the relevance of this measurement clinically, if we use the methodology outlined by Ian (above) but don't use loading which approximates subject bodyweight.
    You seem to be saying it isn't relevant?

    Interesting thread!

  16. Sorry, I made an error in terminology in the last posting. "Ankle joint plantarflexion stiffness" should have "read ankle joint dorsiflexion stiffness". I have listed those corrections below from my last posting on this subject.

  17. I think that measuring ankle joint dorsiflexion clinically is very relevant as long as the examiner is consistent in how the test is done. I have the patient supine, put the STJ in neutral, and, with the patient relaxed, use about 20 lbs of force on the forefoot to assess ankle dorsiflexion.

    However, with an individual weighing 180 lbs, is 20 lbs a physiologic load? Certainly not. However, also the patient's muscles are relaxed so that with muscle firing in late midstance, a 180 lb load on the forefoot would produce much less dorsiflexion than with no muscles firing.

    For your demonstrations, David, I think it would be much more interesting for you and your students to perform the test in the following manner. Have the subject supine with the knees extended on an exam table with someway to buttress their shoulders on the table so they won't slide posteriorly. Take a bathroom scale (measures body weight) and then apply a force on the foot with the bathroom scale, parallel to transverse plane to approximate the ground orientation, until you reach 10 lbs (or you may convert to Newtons). Record the amount of ankle joint dorsiflexion at 10 lbs. Next push on the forefoot with 20 lbs, and record the dorsiflexion. Continue this sequence of 10 lb increases and dorsiflexion increases until you reach the subjects body weight or the subject becomes uncomfortable.

    Now plot plantar forefoot load on the Y-axis and ankle dorsiflexion on the X-axis. You will now have generated a load vs deformation curve for that individual's ankle joint. The slope of this curve at any point along the x-axis will then be the ankle joint dorsiflexion stiffness for that degree of ankle joint dorsiflexion. The curve will be concave upward, with the stiffness increasing greatly as the dorsiflexion angle is increased.

    This study on 50 subjects would be an excellent research project to be published in JAPMA.
  18. Philip Clayton

    Philip Clayton Active Member

    Hi Kevin
    As much as I appreciate the ingenuity of the bathroom scales for research I can't help wondering how many hands I will need in my solo practise, not withstanding any issues of parallax but I am sure after a few pints it will be great fun trying and even more fun watching. Now where did I put my tractograph and my xxxx beer?

    Great ideas, seriously.

  19. Clinical practice and performing scientific medical research are too very different and distinct entities. These entities are complementary of each other, both needing the other to improve the theory, knowledge and treatment methods of the practicing clinician for their patients.

    Clinical practice without research dooms the clinician to endless speculation since there is no ability to gain knowledge from experimental data. As a result, the clinician will be hindered at developing accurate treatment theory and at providing better treatment methods for their patients due to the lack of research knowledge.

    Scientific medical research without the relevant and practical interaction from the clinical realm, will result in useless and meaningless information for the clinician. Since the ultimate providers of care to patients are the clinicians, researchers need to have clinical contact to be certain that their research is clinically relevant so that it can effectively provide the clinician with usable information that may ultimately benefit the patient.

    If you are interested in more thoughts in this regard, Philip, you may want to read an article I wrote a few years ago on this same subject (Kirby KA: What future direction should podiatric biomechanics take? Clinics in Podiatric Medicine and Surgery, 18 (4):719-723, October 2001).

    That is, after you get done playing with your tractograph, bathroom scales and drinking your xxxx beer. ;)
  20. David and Ian:

    Here is a hypothetical set of load vs deformation curves of ankle joint dorsiflexion that may be obtained using my described bathroom scale test on a subject with "normal" ankle joint dorsiflexion and on a subject with an "equinus condition". Note the horizontal offset to the left of the load vs deformation curve for the "equinus condition". Also note that at equal magnitudes of ankle joint dorsiflexion stiffnesses in these two hypothetical individuals, that in the normal foot this stiffness occurs at 8 degrees of dorsiflexion and in the equinus foot this same magnitude of stiffness occurs at 4 degrees of plantarflexion. These types of load vs deformation curves of ankle joint dorsiflexion stiffness have much more biomechanical significance than our clinical measurements or ankle joint dorsiflexion at one single plantar loading force when it comes to understanding the passive forces and plantarflexion moments generated by the subject during the late midstance stage of walking gait.

    I hope that you can see that by the plotting of data points to produce a load vs deformation curve of a few subjects with different "degrees of ankle joint dorsiflexion", using my suggested "bathroom scale experiment", will provide both you and your students with much more mechanical information regarding the biomechanical effect of differences in the load vs deformation characteristics of the ankle joint. This load vs deformatoin information of the ankle joint, when correlated to the measurement of ankle joint dorsiflexion we perform in a clinical setting, will give both the researcher and clinician a better appreciation of the mechanics of the ankle joint.

    Attached Files:

  21. davidh

    davidh Podiatry Arena Veteran

    Hello Kevin,

    I like the idea for a research project (like too the fact that scales can be used which are accurate and calibrated). I can see a problem in deciding whether the STJ is in neutral or not, because as we all agree, this makes a big difference in the ability of the foot to dorsiflex past the 90-degrees to the leg mark.

    Thanks for your answer.
    Much appreciated!


  22. David:

    Glad you like my idea. Actually I proposed a similar experiment about 5 years ago on the podiatry mailbase but it didn't seem like anyone understood, at that time, about this load vs deformation concept of the ankle joint, and my idea didn't generate any interest. It greatly pleases me that you, and a few others on this list, see the utility of such an experiment and its potential to help us with our understanding of ankle joint and foot biomechanics.

    Your comment regarding STJ neutral is a good one and this may be one of the greatest technical difficulties of performing such an experiment. The way I would probably approach it is to not try and position the STJ in neutral position but rather let the bathroom scale platform, held in a position parallel to the transverse plane of the subject to simulate the ground, determine the STJ rotational position.

    In other words, when the bathroom scale first registers 10 lbs (or you could use 40 N) when the forefoot is loaded, take note of the STJ rotational position that the patient's foot has assumed and then try to make sure that with continued incremental loading of the forefoot that the STJ stays in that position. This will be easy with feet that have relatively normal STJ spatial location. However, the foot will tend to pronate further with increased forefoot loading if the foot has a significantly medially deviated STJ axis and may even try to supinate with increased forefoot loading if the foot has a signficantly laterally deviated STJ axis.

    The other experimental option is to simply let the STJ rotate freely under the increasing forefoot loading which is probably a much more realistic method of how the foot and ankle respond to forces within the critical late-midstance phase of walking gait. As I said, if you want to do a very nice experiment, taking note of STJ rotation during increased incremental loading of the forefoot will likely be found to correlate to STJ spatial location and, more specifically, to the position of the Achilles tendon relative to the exit point of the STJ axis through the posterior calcaneus. The more of a supination moment arm that the Achilles tendon has relative to the STJ axis, then the less likely the foot will pronate with forefoot loading. The smaller the supination moment arm of the Achilles tendon, the greater the foot will pronate with forefoot loading. Of course this will be balanced by the location of the center of pressure (CoP) on the forefoot (from the bathroom scales)relative to the anterior spatial location of the STJ axis. These certainly could be used as another measurement parameter that could easily be used as data to produce a second paper for publication.

    You must remember that what are measuring is not just the load vs deformation characteristics of the ankle (i.e. talo-tibial) joint but also the load vs deformation characteristics of the rearfoot and forefoot also. A foot with a stiff ankle joint but a compliant MTJ and midfoot will show more forefoot dorsiflexion on the rearfoot when the forefoot load is increased. A foot with a compliant ankle joint and a stiff MTJ and midfoot will show more ankle joint dorsiflexion and less forefoot dorsiflexion when the forefoot load is increased. This will likely correlate to those feet that show increased late midstance pronation in gait since, in these feet, the medial column has signficantly less dorsiflexion stiffness than the lateral column so that at increasing forefoot loads there is a relative lateral shift in the CoP which will cause increased magnitudes of STJ pronation moment, late midstance STJ pronation and medial arch flattening motion. With this in mind, maybe we should call the measurement ankle-foot dorsiflexion stiffness rather than ankle joint dorsiflexion stiffness, since we are not able to detect talar motion within the mortise and are using the plane of the forefoot as our distal reference of ankle joint motion.

    As you can see, David, I have a lot to say on this subject and I could go on and on if I had the time now. I would be happy to help you further with this project and maybe, if you are interested, we could do so on a private e-mail basis for further discussion.
  23. Philip Clayton

    Philip Clayton Active Member

    Hi Kevin
    Is the example of using the scales working in just the sagittal plane on a joint that moves through three planes and not relating to time, cadence, stride length, better performed using pressure sensitive computerised gait analysis. Surely the relative stiffness will alter when on of these or other conditions is applied. Muscle strength, tendon laxity and general proprieception triggers must also play there part along with the patients foot wear. I have personally seen a patient with the 'stiffest' ankle joint be massaged and manipulated for 20 mins to end with a fairly normal ROM. When do we measure the patient? AM PM before or after warm up? Before or after exercise? after manipulation?
    I applaud any new approaches and look forward to the data and subsequent new techniques to lessen the art and strengthens the science. The lack of precision and reproducable measurements has endlessly frustrated me. The tools of our trade are quite pathetic. How can we continue with a science that enables our unwitting patients to accept that where ever they decide to be examined, the chances of any other practioner reproducing the same diagnosis, measuremant and eventual treatment /device being extremely low? The pursuit of these new descriptions and re-evaluations of our subject can only be a good thing but must be accompanied by a comprehensive re-training and introduction of apparatus that is affordable and can withstand the riggers of examination by both experts and our peers.
    I am sure a good research project would be to send 'dummy' patients (Ian will no who I mean) to hundreds of different practioners acroos the globe to discover what the level of reproducable results are ther for a complete biomechasnical examination and maybe to record the areas of best practise and then pass it on.

    12.10 almost brain dead through lack of sleep and children who 'hog' the computers, thats my excuse...sad isn't it....

  24. davidh

    davidh Podiatry Arena Veteran

    You wrote
    "As you can see, David, I have a lot to say on this subject and I could go on and on if I had the time now. I would be happy to help you further with this project and maybe, if you are interested, we could do so on a private e-mail basis for further discussion."

    Rather than doing a simple (n = 50) study, which really doesn't excite me, since the cohort is so small, we could perhaps instead look at a multi-centre study?

    With the number of pods on this forum who have some research experience, I'm sure we could make up perhaps 10 or 15 Centres (perhaps more)from which to carry this out?

    I'd be happy to liaise with yourself and whoever to formulate the hypotheses and methodology, and to supervise work here in the UK Midlands.

    Anyone else interested?

  25. I actually think that there is a distinct advantage to having one researcher supervise all parts of an experiment of this sort....consistency. Since the experimental technique will greatly affect the results, I doubt this could be easily done in a multi-center trial with great consistency in technique. Maybe you have had different experiences in this regard?
  26. davidh

    davidh Podiatry Arena Veteran

    Hi Kevin,

    I have no experience of muti-centre trials, but if the protocol were sufficiently tight I don't forsee many problems.

    The real problems will be in working out a protocol which will allow each data collector to gather valid data, and in such a quantity as to become meaningful.

    My own experience, using a purpose-built rig to hold the lower leg secure so that coronal plane movement at the ankle joint complex could be quantified - we used a "floating" footplate and a measured amount of torque to induce movement - is that 100 normal subjects will not allow for variability in the normal lower limb. In this particular study (n=100), a Shapiro-Wilk test showed a non-normal distribution.

    The lower leg rig was an adaptation of the rig described in
    J Biomechanics Vol 26, No 1. pp. 69-76. 1993.

    Incidentally, we did a mock-up of the leg-cage of this particular rig, and how they got it to cut out unwanted transverse-plane movement in the lower leg beats me!

    The other problem we all face when doing scientific data collection on living biological entities, is one of diurnal variation
    (Measurement of stiffness in the metacarpophalangeal joint: circadian variation. Yung P, Unsworth A, and Haslock I.
    in Clin. Physiol Meas. 1984, Vol 5, No 2, 57-65.
    But this of course could easily be written into a protocol.


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