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101 things I ought to know but have been too embarrassed to ask.....

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Mark Russell, Nov 7, 2006.

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    Sometimes the simplest things in life just seem to pass by unnoticed and it's not until much later you think, 'now why is that so?' I'm sure most people have a question or two on something they've missed about basic biomechanic principles but are maybe a little hesitant about asking. I have a few..

    1. During propulsion the foot functions as both a shock absorber and rigid lever. During pronatory moments it is the former, during supinatory moments it is the latter. What mechanisms are involved to effect this change?

    2. 65% of all new female patients in my practice in the age range 40 - 65 years present with functional hallux limitus, which responds well to local manipulation, increasing the ROM by >20 degrees. Manipulation is by extending the hallux through the MTPJ and maintaining position for 45 seconds without cavitation. Why does this work?

    3. What stretching exercises are best to increase ankle joint ROM?


    Mark Russell
  2. Ian Linane

    Ian Linane Well-Known Member

    Hi Mark

    You asked:

    3. What stretching exercises are best to increase ankle joint ROM?

    I do not know if you are focusing on plantar and dorsiflexion Mark or if you are looking to alter other movements as well. The following is my preferred approach for what it is worth.

    Mechanically, I approach increasing the ankle joint rom by looking to improve the whole AJC rom. To achieve this I tend to use peripheral mobilisation techniques upon the talar crural joint, the subtalar joint, the distal fibular head and, in addition, tend to mobilise the proximal fibular head as well.

    It is suprising how much rom increase can be achieved in the ankle joint by these techniques before even having to consider stretches to gastroc and soleus. Indeed I have to consider Gastroc and Soleus less often than I use to (often as pods we have focuse to much on them perhaps).

    One of the clinical checks I use when applying this technque is precisely observing how much weightbearing knee flexion is attainable pre and post treatment. This is always the start point on additional treatments. Often two or three session establishes the improvement for quite some time.
    They are very simple movements within a patients control and even one session often brings considerable improvement to the patient.

    Soft tissue wise, again the joint mobs often restore some of the patterning actions of muscles and so I tend to provide soft tissue mobs to the ankle ligaments if needed.

    I'm sure the more physio minded folks will come up with different or better methods. From my Pod perspective these are simple and effective for what I want. Occassionally I may provide some mobs to the knee as well.

    Although I am able to provide more high velocity manipulative techniques I much prefer the mobs.

  3. Thanks Ian. I asked this as I noticed that many patients have limited ankle dorsiflexion, some without any at all, and I wonder how effective devices will be if ROM is restricted. Not sure I understand fully the difference between manipulation and mobilisation or indeed what high velocity techniques are, but I have started inverting the foot when stretching the TA by having the patient stand on a wood wedge and this seems to be more effective than just the straightforward 'push the wall' stretch.
  4. davidh

    davidh Podiatry Arena Veteran

    Hi Mark,

    Re: The foot as a shock absorber and rigid lever.....
    heel strike.
    At heel strike the foot is inverted (witness your own heel strike pattern which will most likely be outside border), everting as it contacts the ground - to ensure a good fit with the ground. This is important for support and ambulation on uneven or soft surfaces. also, this is your "loose bag of bones" or shock absorber.
    At midstance the opposing limb is moving forward of the stance limb and this has the effect of turning the pelvis (in the transverse plane) and rotating the stance limb outwards - raising the arch and causing a truss effect in the tarsal bones. You can see this with a vertical loading system in the COP, which in most healthy subjects moves laterally, then medially.
    At late midstand and...
    The windlass effect comes into play too, and this further tightens the foot, converting it into a lever for push-off.
    BTW you can't have a biological "rigid" lever, but that's another story :cool: .

    Great end of wild trout season BTW, last day was 7 fish to size 14 Hares Ear (type of fly, for those who don't know) fished upstream in about 9 inches of water. Best fish slightly over 2 lbs. All fish returned fit and healthy!

  5. Ian Linane

    Ian Linane Well-Known Member

    Hi Mark

    "...difference between manipulation and mobilisation"

    My loose explanation of the difference, based around Maitland,

    Mobilisations are a practitioner applied, oscillatory movement
    technique always within a patient’s control. The patient is passive

    Manipulations are a high velocity, small amplitude, practitioner
    applied technique outside of a patient’s control. The patient is
    passive throughout

    (cf Maitland’s Peripheral Manipulation, 4th edition, pp26)

    With mobilisations you are working with grades of small amplitudes of oscilatory movement throughout the whole range of movement of a joint. You work through Grades 1-3 which are often within the range of movement a patient can actively take their joint. Grade 4 is that end range of movement often practically unattainable to a pt but that they have physiological ability to achieve. At grade 4 the movements are gentle and very small amplitudes of oscillation. The patient can stop these movements at any time. Through out each mobilisation you check and recheck the level of improvement gained.

    So, for example, to increase ankle dorsiflexion I would assess the wb ability of the pt to flex their knee over the foot. Then I might take the talo crural (realise I spelt this wrong on the previous post) joint through a postero-anterior mobilisation, grades 1-4, (matter of seconds or minutes), then reassess their knee flexion capability. I have probably gained some. Now I might repeat the same treatment immediately or add another one to it.

    My own experience has been to see reasonable rom improvements quite quickly in the one session. Pt can be taught how to do exercises that might help to help maintain the flexibility increase.

    Manipulations often involve a high velocity thrust that is beyond a patients control. I find the mbilisation release lasts longer.

    I do both but the manipulations are a much less frequent use.

    Happy to PM you with more details and can certainly recommend them. They form a natural part of any biomech work I do as well as serving as stand alone treatment.

  6. Craig Payne

    Craig Payne Moderator

    That has been a long held assumption, but two published research projects (sorry, no have refs handy) show that that rearfoot pronation/supination does not affect shock absorption, so its another of those podiatric myths.

    One study looked at shock transmitted through to tibia while running on cambered rd (ie one foot pronates more while the other foot pronates less) and it made no difference.
  7. efuller

    efuller MVP

    A lot of the theory behind this comes from elftman and Manter and the lining up of the axes of the talonavicular and calcaneal cuboid joints. Van Laangalan's thesis rips this idea to shreads. Manter had to reverse Elftman's axes to make it work and has essentially misquoted Elftman. Everyone else, includeing Root Orien and Weed perpetuated the misquote. Finally axes cannot limit motion because they are imaginary lines. So, in addition to the experimental evidence that Craig mentioned, the theory behind the idea is flawed.

    However, the measurments of arch height during walking do not take into account "normal" motion of the joints as opposed to abnormal motion of the joints. Normal motion, in this context, is motion that occurs with minimal load and the motion stops when the normal end of range of motion is reached. The end of range of motion can be ligamentous ie abduction of MPJ or it can be bony ie maximal pronation of the STJ when the lateral process of the talus hits the floor of the sinus tarsi. At the end of normal motion, further motion can be achieved with additional load and the motion would be related to the type of structure resisting further motion.

    The STJ is interesting in that in some feet it acheives an equilibrium positioin that is not at the end of its normal range of motion. In gait, it could achieve an equilibrium position that is not at the end of range of motion and then further into gait, the pronation moment acting on the joint could increase and the subtalar joint would pronate to the end of its normal motion. (aka late stance phase pronation.) Late stance phase pronation could be within the normal range of motion of the joint, but it would make the foot appear non rigid. I would caution about using an arch rigidity measurement that used an arch collapse measurement that didn't take this normal motion into account.

    That said, I still think the rigid lever mobile adapter theory of the foot is bunk. If you look at Nigg's and Bobbert's work on impact with running, they have shown that the majority of shock absorption occurs at the knee. There is also some energy absorbed with ankle plantar flexion at heel contact.


    Eric Fuller
  8. Good posting, Eric. While I will agree that it is true that Eftman's idea of two talo-navicular axes and two calcaneo-cuboid joint axes that were based on "the eye of a connoisseur" has been misinterpreted by nearly everyone that quoted from his paper, including Mann and Root et al, Elftman did make some very good points in his paper (Elftman H: The transverse tarsal joint and its control. Clin. Orthop., 16:41-44, 1960).

    In fact, Elftman thought there was only one transverse tarsal axis (MTJ axis).
    Here are the quotes I pulled out of Elftman's paper for my presentation at the PFOLA meeting in Chicago in a few weeks:

    Considered MTJ axis to change in spatial location when STJ rotates from pronated to supinated:

    “In passing from the pronated to the supinated position there is a continuous change in the positions of the significant joint elements and, consequently, of the instantaneous transverse tarsal axis.”

    Considered cuboid and navicular to be one rigid body:

    “Although the cuboid and the navicular are not completely rigidly attached to each other, any relative movement between them is so minor that we are entitled to consider these two bones as moving together as a first approximation.”

    These are the exact conclusions that Nester et al made in their midtarsal joint paper (Nester CJ, Findlow A, Bowker P: Scientific approach to the axis of rotation of the midtarsal joint. JAPMA, 91(2):68-73, 2001) over 40 years later.

    In my reading of Elftman's paper a few times over for this lecture, it is hard to find anywhere in the paper where he concludes that "opposing axes" cause "a restriction of motion" at the midtarsal joint. I think this is one of those continuing podiatric/orthopedic myths that has been perpetuated over the ages by other authors who have not taken the time to clearly read and understand the words of the original author. But certainly this concept is somewhat implied by the drawings he has done, but not specifically stated as such in the paper.

    However, in regard to the mobile adapter/rigid lever theory of the foot, I will need to disagree here. I do think the foot is uniquely constructed so that it will be more mobile in early stance phase and will be more rigid in late stance phase. And this is a very important mechanism for the foot and the body as a whole. Contrary to what is taught in nearly all podiatry schools, this mechanism is not caused as much by pronation/supination of the STJ as it is caused by the mechanical necessity of the Achilles tendon tensile forces and plantar ligament tensile forces to be simultaneously increasing rapidly in magnitude as the forefoot is loaded by increasing magnitudes of GRF in late stance phase.

    In other words, I believe the mobile adapter function of the foot in the first half of stance phase and rigid lever function of the foot in the latter half of stance phase is caused by the rapidly increasing tensile forces within the Achilles tendon, plantar aponeurosis, and plantar ligaments (with contributions also from muscular contractile forces from the plantar intrinsics, PT, FDL, FHL, and PL) that occurs as GRF rapidly increases on the plantar forefoot. These rapidly increasing plantar ligament/fascia tensile forces cause a rapid increase in forefoot plantarflexion moments and midtarsal/midfoot joint compression forces that helps the forefoot resist dorsiflexion moments as the forefoot is loaded by increased GRF. In essence, this "automatic rigid lever mechanism" increases forefoot dorsiflexion stiffness.

    Therefore these "automatically occurring forces" cause the foot "to have no other option" but to become "a more rigid lever" during late midstance and propulsion because of its unique construction where the plantar ligaments are made more stiff by the increased tensile force they are subjected to as they resist longitudinal arch elongation. Of course, the rigid lever effect assumes that the medial longitudinal arch of the foot is not severely flattened and the talo-navicular joint is sufficiently superior to the calcaneo-cuboid joint (i.e. STJ axis is not severely medially deviated) so that the tensile forces rapidly developing within the plantar fascia will have sufficient forefoot plantarflexion moment arm (i.e. sufficient distance from plantarfascia to talo-navicular joint). With sufficient forefoot plantarflexion moment arm, the rapidly increasing plantar fascial tensile forces has a better mechanical ability to prevent forefoot dorsiflexion motion than if the medial arch were flat. If the medial arch is excessively flat then the resultant increased magnitudes of plantar fascial tensile forces will cause excessive elongation of the plantar fascia and therefore will allow increasing forefoot dorsiflexion that will, in turn, result in decreased forefoot dorsiflexion stiffness in late midstance.

    I have written a Precision Intricast Newsletter about this mechanism a few months ago and it seems like an important enough theory to consider publishing it as a journal article.
    Last edited: Nov 8, 2006
  9. efuller

    efuller MVP

    Kevin, I agree with you that foot can function as a mobile adapter as you describe above. I also agree that this adaptation is independent of STJ position. My point was directed at those who take the lining up of the axes theory and attribute STJ pronation to shock absorption. You are right, adaptation is different from shock absorption.

    Last edited by a moderator: Nov 8, 2006
  10. Eric:

    Glad you agree. That makes me feel better. Someday we will have to find something we can disagree on (about biomechanics) so we can have a really lively discussion. ;)
  11. Berms

    Berms Active Member

    On that note, there are also a few questions about "posterior tibial tendon dysfunction" that I'd like to bring up :confused:

    1. How is PTTD diagnosed?
    2. How is PTTD measured?
    3. If you reach a diagnosis of PTTD how is best managed / treated?

    Cheers, Adam
  12. Admin2

    Admin2 Administrator Staff Member

    Start here:
    Posterior tibial tendon dysfunction
    Primacy of PTTD
    Os navicularis syndrome vs Post Tib tendon dysfunction
    Gliding resistance of the posterior tibial tendon
    Gait changes with tibialis posterior dysfunction
    Article in Podiatry Today on Adult Flatfoot
  13. PodAus

    PodAus Active Member

    Hi Kevin,

    A concise explaination.

    The pattern of plantar prioprioceptive input is dependant upon the pattern of associated GFR's, and is related to the body's 'muscle memory' during WB activity. Much of the neurological & mechanical output during activity is reactionary, but how much is predictory? Do we understimate the central and peripheral neurology whilst focusing on gaits' resultant motion?


  14. Adam:

    I was invited to write an article on posterior tibial dysfunction by Podiatry Management Magazine six years ago (Kirby KA: Conservative treatment of posterior tibial dysfunction. Podiatry Management, 19:73-82, 2000). Your questions are answered in the article. I would be happy to provide you with a copy of the article in pdf format if you send me an e-mail privately.
  15. daisyboi

    daisyboi Active Member

    Not sure that I grasp the idea of mobilisations/manipulations being within or outwith the patients "control" Ian. My understanding of the difference are that mobilisations are movements which do not extend the ROM into the paraphysiological space whereas manipulations do - hence the often associated cavitation.

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