Announcement

Collapse
No announcement yet.

Pronation summary

Collapse
This topic is closed.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Pronation summary

    Dear Biomch-l,

    Thanks for the feedback regarding pronation. Here is a summary of all
    the responses. Sorry for the delay.Jason Agosta.

    >Hi,
    >
    >I am a MSc student and a Podiatrist from Olympic Park Sports Medicine
    >Centre in Melbourne.
    >
    >Recently I was asked a question (and now will give a presentation),'How
    >much pronation of the foot is too much?'. My answer was, that there are
    >varying degrees of pronation among individuals as this is related to the
    >alignment of a person's own biomechanics and that everybody adapts to
    >their own biomechanics. Further to this, I mentioned that adaptation is
    >underestimated as many people present with large ranges of motion but
    >have no history of injury.
    >
    >I am interested in other people's response to this question.
    >
    >Thank you in advance,
    >
    >Jason Agosta
    >jasonic@ozemail.com.au

    From:
    kgholt@bu.edu (Kenneth G. Holt)
    To:
    jasonic@ozemail.com.au


    I think you gave a good answer to the wrong question. To elaborate on
    that
    answer further we must consider in more depth the actual biomechanics
    involved as they relate to anatomical structure of the foot and lower
    extremity. Excessive pronation is but one 'symptom' of a structural
    abnormality (e.g. forefoot varus, rearfoot varus in non-weight bearing)
    subject to biomechanical torques when the foot contacts the ground. For
    example a foot that has a combined forefoot varus and rearfoot varus
    abnormality makes ground contact in a more supinated position, leading
    to a
    longer moment arm and increased torque as the foot rotates around the
    subtalar, transverse-tarsal, and talocalcaneal-navicular axes. This
    may
    lead to excessive stresses on medial tissues (e.g. post tib, plantar
    fascia) and potentially cause injury to them. There may be no
    'excessive'
    pronation at all, and/or the breakdown of medial tissues may lead to
    excessive pronation. Another potential scenario: ground contact of the
    forefoot may take longer because it has a greater range of motion to
    move
    through. This may result in late pronation (again not necessarily
    excessive) that may disrupt the normal functioning of pronation and knee
    flexion, perhaps resulting in patello-femoral pain.

    One must also take into account other risks that are associated with
    potential injury and intensify any structural/biomechanical problems
    (e.g.
    obesity, exercise patterns, prior traumatic injury etc...).

    There are a number of other causes for common non-traumatic injury (e.g.
    bunions, ankle sprains, hammer toes, shin splints, achilles tendinitis)
    due to the combined effects of structural abnormality, anatomic function
    and biomechanical factors on ground contact without excessive pronation.
    The major excess in pronation is the use of the term. I would refer you
    to:

    Holt, KG., & Hamill, J. 1995. "Running Injuries and Treatment: A
    Dynamic
    Approach." In G.J. Sanmarco (Ed.) Rehabilitation of the Foot and
    Ankle.
    Mosby

    As an aside, I would argue that those who prescribe orthoses without
    understanding these important relationships are illserving their
    patients,
    and giving orthoses a bad name when they are inappropriately prescribed
    as
    a result.

    From:
    Ned Frederick
    To:
    jasonic@ozemail.com.au
    References:
    1


    My asking the question as I did, "What defines too much ?", was an
    attempt
    to get at a problem with your request. When you ask how much pronation
    is
    too much you imply that there is something intrinsically bad about
    pronation beyond a certain level... but you don't tell us what! I can
    assume from your podiatry training that you are refering to overuse
    injuries either caused or exaccerbated by excessive pronation. I think
    you'll find that many scientists , myself included, are skeptical about
    that link.
    Until we can prove that there is a direct cause and effect
    relationship between pronation and a particular injury, and until you
    define what that injury is then your question will be a tautology.
    Let me give you an example. If medial ankle sprains were the
    undesired result, then you would get a different value for "excessive"
    pronation or calcaneal eversion than you would if patellofemoral syndrom
    were the undesired result.
    We both know that pronation is good and desireable for many
    reasons. So, what is the outcome you are trying to avoid by limiting
    pronation (or defining a limit)?

    >Hi Ned,
    >
    >Thank you for your response regarding pronation. Your question of "What
    >defines too much?", is exactly what I was getting at. Answering the 'How
    >much is too much' question I mentioned that all people for different
    >reasons present with varying degrees of motion and that this may or may
    >not be relevant to injury.
    >
    >Regards, Jason Agosta

    From:
    Irene S McClay
    To:
    Nicky & Jason


    Hello,

    There are two ways to describe excessive pronation. The first is based
    upon the mean and sd found in the normal population and determining some
    criteria (ie. 1 or 2 sd above the mean) that defines excessive. Now
    excessive
    pronation does not always result in problems/injury. And often subjects
    with injury exhibit normal pronation values. The other way to describe
    excessive is that amount which causes a problem (based upon person's
    mechanics, structure, etc). I prefer the first definition because it is
    more clearly defined. If you are 2 sd above a population mean, then you
    have a basis for which to state something is excessive. If someone
    exhibits 12 degrees of pronation - and is having problems - I would not
    state that it was from excessive pronation. If I was sure the problem
    was
    related to the pronation movement - then I would state the patient was
    unable to tolerate a normal amount of pronation (for whatever reason).

    I also think that people need to be precise in describing where the
    pronation occurs. In research, we are most often looking at rearfoot
    (due
    to the difficulty in accurately tracking true midfoot motion. Midfoot
    motion is typically assessed subjectively. Therefore a person could
    have
    12 deg (a normal amount) of rearfoot eversion, but be collapsing in the
    midfoot region (which would be excessive midfoot pronation). So their
    problems would be related to excessive midfoot pronation in the presence
    of normal rearfoot pronation. Thus - further confusion.

    This would be a great topic for the Foot list that has recently
    developed. The address is foot-l@lists.nau.edu. It would generate some
    interesting discussion.

    Irene McClay, PhD, PT
    Motion Analysis Laboratory
    305 McKinly Lab
    University of Delaware
    Newark, DE 19716

    From:
    Irene S McClay
    To:
    Nicky & Jason


    Jason,

    Why do you think that would be difficult? We did just that - collected
    data on 100 runners and found a mean peak of approx. 12 deg with a sd of
    approx. 4 deg.

    Irene McClay
    From:
    Irene S McClay
    To:
    Nicky & Jason

    Jason,

    We used a sample of 100 asymptomatic runners.

    Irene McClay

    From:
    David MacPhail
    To:
    jasonic@ozemail.com.au


    G'day Jason,

    I agree with your answer re adapation. This process is essential for
    bipedal
    survival. Otherwise, I doubt if we've be here to discuss the issue. I
    have a
    paper somewhere that supports your postion. I'll try and locate it over
    the
    weekend.

    Cheers,
    David

    From:
    Ned Frederick
    To:
    jasonic@ozemail.com.au


    What defines "too much" pronation?

    From:
    Footform Labs
    To:
    "'jasonic@ozemail.com.au'"


    Jason,
    I agree with you completely. My theorey on this is, "if it
    works, don't fix it." If a subject has no pain or problems, their
    condition is normal. If a subject develops problems and orhotic therapy
    is designated, I still think that the patients "normal" should be the
    baseline for orthotic alterations. I developed a process called Dynamic
    Plantar Modeling that provides you with a physical look at what is
    "normal" for your subject. When it comes to therapy, instead of
    radically positioning the foot to a textbook position and modeling it,
    I prefer to model what is normal and provide the minimum alteration to
    this normal anatomy for symptom relief. Chek out the Science html on my
    website. www.footform.com/science.html I believe we think alike on
    this subject.
    Randall Barna
    Pres. Footform Labs

    From:
    Craig Payne
    To:
    jasonic@ozemail.com.au

    This topic has been discussed ad nauseum on the podiatry list - check
    the
    archives.

    Kind Regards
    CP

    From:
    "V.BALTZOPOULOS"
    Organization:
    ALSAGER, CREWE+ALSAGER FACULTY, MMU
    To:
    jasonic@ozemail.com.au


    Dear Jason

    I agree with your view about individual variations but furthemore
    in my opinion the amount of pronation may be not as critical as
    when it occurs in the stance phase. Even "normal" degree of pronation
    occuring late in the stance phase is likely to cause
    excessive internal tibial rotation that will affect pattelo-femoral
    mechanics.
    I hope this view helps the debate on how much is too much pronation?

    V. Baltzopoulos

    Biomechanics Group
    Manchester Metropolitan University
Working...
X