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Stiffness of surface and symptoms

Discussion in 'Biomechanics, Sports and Foot orthoses' started by markjohconley, Dec 17, 2013.

  1. markjohconley

    markjohconley Well-Known Member

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    If a patient reported walking on 'hard' surfaces caused pain in their feet whilst no such pain on 'soft' surfaces, is it logical to conclude that it is soft tissue that is being stressed rather than bone, and vice versa?
  2. footdoctor

    footdoctor Active Member

    Hi mark.

    What structure do you think is affected in this patient?

  3. Not necessarily, it depends how the body regulates leg stiffness.

    but what you need is a diagnosis of what is hurting and then look at why
  4. Both soft tissue and bone may experience increased internal stresses when walking on hard surfaces. Soft tissue will deform more and bone will deform less for a given ground reaction force due to their differing Young's modulus. The most likely tissue to be injured is the one that is first to undergo plastic deformation.
  5. I generally concur, however, there may be something in the frequency of the shock wave versus the resonant frequency of the tissues too- think fat female opera singers and glasses smashing...

    Then think Clifford Richard: http://www.youtube.com/watch?v=sn9mLnKmPco (maybe not).
  6. Orthican

    Orthican Active Member

    Have you done a lunge test? What tissues are stressed? For a limb to have pain in the foot while walking on hard surface but not on soft smells of a limb stiffness issue does it not?
    There will be less forgiveness of the stiff limb on the hard surface and more forgiveness of the stiff limb on the soft surface where loss of talocrural ROM is concerned. Would this not increase the force applied at the plantar surface when on a hard walking surface with a stiff limb and be less so on a soft surface?

    Just thinking out loud.
  7. markjohconley

    markjohconley Well-Known Member

    Morning Scott, this particular lady, apart from being affected "between the ears"; I haven't been able to replicate the pain by joint movements nor resistance against muscle action. I'm attempting to get some soft-tissue imaging done on the foot, mark
  8. markjohconley

    markjohconley Well-Known Member

    Thanks Mike, not the answer I was hoping; stiffness, a difficult concept to grasp, all the best, mark
  9. markjohconley

    markjohconley Well-Known Member

    Goodaye Orthican, apart from "Total Knee Replacement" patients I always do a lunge test. This 'lady' had greater than 30deg bilaterally. A merry Xmas to you and family, mark
  10. It is difficult to understand, Mark. Luckilly, stiffness is the old black and energy is the new. ;):santa2::santa: Anyway, put a soft surface under her feet and the problem should be solved- right?
  11. markjohconley

    markjohconley Well-Known Member

    Goodaye Simon, and luckily i'm about to retire; until then i'll do my best to follow the threads. The 'stiffness' issue seems to be discussed by a limited number of clinicians, are the rest of us so far behind?
    As for orthoses, that's what I've done, she was happy (with me not so her doctor), all the best to you and your family
  12. Mark:

    Stiffness of surfaces and stiffness of the lower extremity is not too difficult to understand since the concept of stiffness in surfaces and in the lower extremity is identical to how other familiar materials or objects are graded as to their stiffness or compliance (the inverse of stiffness is compliance).

    Let's say you have two fishing poles, pole A, used for deep water fishing that doesn't bend very much with a 2 pound fish hanging from the line, and pole B, an ultralight pole that will bend very much with a 2 pound fish hanging from the line. Now, which one would you describe as being a stiffer pole? Pole A, of course, since it deforms less for a given load than pole B. Pole A would be said to be stiffer than pole B, or, alternatively, pole B could be said to be a more compliant pole than pole A.

    When we talk about the stiffness or compliance of any material or object we are describing what is called its load versus deformation characteristics. In other words, stiffer materials deform less than do more compliant materials for a given external loading force. Alternatively, if a stiffer material deforms the same amount as a more compliant material, we would know that the external loading force acting on the stiffer material is greater than the external loading force acting on the more compliant material.

    In the lower extremity, there are a few conventions by which to measure lower extremity stiffness (often called leg stiffness) during running. One of these methods is to measure the peak ground reaction force (GRF) and divide it by the vertical displacement of the center of mass (CoM) of the runner ( (McMahon TA, Cheng GC: The mechanics of running: how does stiffness couple with speed? J. Biomech, 23(Supp. 1):65-78, 1990). Again, this is simply a load versus deformation problem where runners who hit the ground harder with more GRF and have less vertical CoM displacement are defined as having stiffer lower extremities during running than those runners who have less GRF and more vertical CoM displacement.

    Even though these concepts are well-understood by too few clinicians, the concept of stiffness has become a relatively common measurement parameter in human and animal locomotion biomechanical studies over the past two decades. I have included a discussion on these topics in a few newsletters on running biomechanics in my new book to soon be published (Kirby KA: Foot and Lower Extremity Biomechanics IV: Precision Intricast Newsletters, 2009-2013. Precision Intricast, Inc., Payson, AZ, 2013).

    And, by the way, I wouldn't consider stiffness either an old concept or one that is being replaced by other concepts. Rather, the increasing use of "stiffness" by clinicians to describe the load vs. deformation characteristics of materials and joints of the body is simply the forward progression of biomechanical concepts being used in a more widely-accepted fashion by a wider range of medical specialties that treat mechanically-related disorders of the human body.

    Hope this helps.:drinks
  13. markjohconley

    markjohconley Well-Known Member

    Thanks Kevin excellent; so if the GRF and vertical displacement of the CoM were known then this would help determine the thickness, the arch configuration (height) and material the orthoses should be made from; and I've just asked the good wife to get me that next book of yours for my next birthday, mark
  14. HansMassage

    HansMassage Active Member

    You can hear the difference between a stiff leg and a compliant leg. When I hear my wife coming down the hall with a clip clop I know it is time for another treatment.

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