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Is there an easy way to calculate RCSP?-student question again

Discussion in 'Biomechanics, Sports and Foot orthoses' started by podstudent2, Aug 6, 2009.

  1. podstudent2

    podstudent2 Member

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    question answered
    Last edited: Aug 7, 2009
  2. Craig Payne

    Craig Payne Moderator

    Like your other question, I can't believe that this is still being taught. We stopped doing that kind of stuff last century.
  3. davidh

    davidh Podiatry Arena Veteran

    Hi Kona,

    You seem to be working from very old material:rolleyes:

    Where are you located?
  4. podstudent2

    podstudent2 Member

    im a second year pod student in the states, and i have no idea whats out dated or not. its brand new to me, and its kicking my-----.

    all i know is i have to master this way of learning. like, now.

    so, how can i calculate rcsp ? is there an equation for it, like there is for stjnp?

    some people can visualize it by the numbers. like "oh! if i calculate NCSP to be a 2 varus, my forefoot is off the floor 6 varus, and my maximally pronated stance is 5 degrees everted, OF COURSE my RCSP is 4 everted! duh! "

    but i can't , so if anyone learned this the old school way and can show me a method that will get me thru an exam, please, help :bang: becuase i can do the math, but when it comes to that last part its hit or miss for me.
  5. Donna

    Donna Active Member

    Hi Kona,

    I work in a biomechanics only practice in Brisbane, where our standard procedure is to take quite detailed biomech assessments. :hammer:

    The only way that we calculate RCSP is through measuring it (using heel & tibial bisection lines & a protractor) with the patient in relaxed stance. I don't know of any way of calculating it with a standard equation... :confused:

    From what I see in analysing the various biomechanical measurements that I take on a daily basis, there are many individual factors (eg. hypermobility/STJ axis location/injury status/etc) that will influence the relationship between RCSP, NCSP, relaxed/neutral tibial angle etc. There is no single equation that will explain everything... if only it was that easy, but we are working with biological (and therefore highly variable) structures.

    You might like to have a look at some of Kevin Kirby's papers including subjects on "Tissue Stress Theory" and "Thinking Like An Engineer" for a more up to date perspective on podiatric biomechanics.


    Donna ;)
  6. podstudent2

    podstudent2 Member

    thanks donna--i wish i had time to read articles, but my exam is tommorow..

    i cant believe there is not a way to calculate RCSP on paper using theoretical values. dont you examine the patient , get thier numbers, and compare by calculation as well?
  7. Griff

    Griff Moderator

    Is this a wind up?
  8. Kona:

    Here is what I did when I was a podiatry student (1979-1983) before the internet became the preferred source of finding examination information for podiatry students:

    1. Attended all the classes I could.
    2. Took notes during the lecture.
    3. Asked questions during the lecture if I didn't understand the material.
    4. Asked questions of the professor after the lecture if I didn't understand the material.
    5. Asked questions of fellow students who may have understood things better than I did.
    6. Studied my notes and the reading assignments well before the examinations.

    I know this may seem old-fashioned, but it worked quite well me. You might want to give it a try sometime.
  9. podstudent2

    podstudent2 Member

    thanks for the advice-

    ive attended all the lectures, asked questions, did all of that. just wondering if there was a way to calculate RCSP that was more straight forward, thats all..

    unfortunately students who do get it, and clinicians who teach, sometimes get things so intuitively that they don't explain things well --in a way a dummy can understand it, lol

    so i came here as a last resort..didn't mean to offend anyone.


  10. Kona:

    Contrary to what you may have been taught, there is no current method by which to accurately calculate the relaxed calcaneal stance position (RCSP) unless some very gross assumptions are made that are not accurate. I would try to get one of your smarter classmates to help you with your question since we don't know what you are being taught by your professors.

    By the way, which podiatry school do you attend and who is your biomechanics professor?
  11. Keiko

    Keiko Welcome New Poster

    hello Kona,

    my uni's biomechanics class was like that too. no matter how many times i had it explained to me or how many problems i did there was always one that thru me off.

    do you have old problems? do as many as you can before the exam.

    unfortunately i dont think there is a calculation that you can plug and chug for the rcsp. that why you examine the patient, lol

    usually it depends on the ff to the floor. ive been told to use your hand on exams, with one hand being yr ncsp (total reafoot) and the other being how far the ff is off the ground. the point is you want the ff to the floor.

    use the ncsp you calculate plus that to determine where it should be, but it depends on each situation.

    you can send me a message and ill try to explain it better

    good luck!:eek:
  12. These biomechanics questions from the US podiatry students reminds me of the time when I took my recertification examination for the American Board of Podiatric Orthopedics and Primary Podiatric Medicine a few years ago. In the exam there were a number of "biomechanics questions" that appeared to be written by the some of the biomechanics professors in the States who hadn't read anything new on biomechanics for the past 20 years.

    Both Larry Huppin, DPM, who had been a student of mine and a Biomechanics Fellow after Eric Fuller and I did the program, spoke about this test after we took it. We both felt that we probably flunked the biomechanics section of the test since we had tried to forget all the "stuff" (this is the nicest word I can think of to describe it) we were taught about biomechanics as students in podiatry school.

    All I can say is we have a long way to go as a profession since I don't think that most podiatry students are being taught current information on biomechanics....for reasons I won't even start to speculate on.
  13. I find it frightening that this is still being taught. Makes me feel like the revolution just passed certain corners by. To quote Bill Hicks: "While some are shouting "revolution, revolution" others are still waiting for evolution "we want our opposable thumbs".

    I'd heard there were problems with biomechanics education in the States, I didn't think it was this bad.
  14. Simon:

    There seem to be problems at many of the schools.....probably relics of another generation?! There is only so much that a few of us who teach the newer ideas can do. :craig::bang: :eek:
  15. efuller

    efuller MVP

    When I was a student there was a large percentage of the class who got an A who felt like they did not understand the materiial. They understood what the instructor was trying get them to answer, but they did not understand how that applied to the real world. Here's the secret, it does not apply in the real world and that is why it is confusing. Well, most of it does not apply in the real world.

    You should talk to your dean about how people who have published recently (The last 15years:rolleyes:) in podiatric publications on the subject of biomechanics believe that what you are being taught is outdated and inaccurate. I would be quite amused to be in on that discussion. It would be a pleasure to help drag podiatric biomechanics into the current century.

    To help you out in your class, try drawing stick diagrams. Draw a vertical line to represent the leg. ( if there is tibial varum draw the line that number of degrees off of vertical. ) Then draw a heel bisection line in various positions that you have numbers for. e.g.calcaneal eversion. (One of the major problems students had with these problems is that they did not understand the definitions of the lines.) Calcaneal eversion is eversion of the calcaneus relative to the leg and not to the ground. So, if you know the relation of the leg to the ground and you know the STJ is in its maximally pronated position, and the amount of eversion available, then you can calculate the relationship of the calcaneus to the ground.

    You cannot calculate RCSP from the numbers that you listed unless you know where the STJ is within its available range of motion. Or you are given a rule that tells you where the STJ is within its range of motion. This rule does not apply to the real world.

    The one major real wordl concept that can be learned from these excercises is the concept of a partially compensated varus (forefoot or rearfoot). A foot that does not have the range of motoin to get the medial forefoot to the ground will tend to have high pressures under the lateral forefoot in stance and early phases of gait.
    Entire semesters were used to essentially teach the above point. Much time wasted.

    "when the STJ goes to end range of pronation, what exactly does that mean? is that equal to the NCSP or?"

    Take a non weight bearing leg draw a line on the leg and heel and move the STJ through its range of motion. Sometimes, the abstract book concept is learned better when you apply things in the real world. The end of the range of motion is a very important concept clinically and something you should be able to have someone locally teach you. It's also relevant surgically as there are surgical plugs that alter the location of the end or the range of motion. You should read Kevin Kirby's paper on the roational equilibrium about the STJ axis. In it there is a nice picture showing the real anatomical cause of the end of range of motion.


  16. Pod on sea

    Pod on sea Active Member

    Hi Craig,
    So what do you teach instead? Are you saying the RSCP is irrelevent? Do you measure subtalar joint motion? In the UK all the orthotic labs ask for the NCSP,RCSP, forefoot deviation, 1st ray position etc. on their prescription forms. Do you do it differently?
  17. Craig Payne

    Craig Payne Moderator

    RCSP is totally irrelevant! What do you think it means? Its a meaningless number. Why would anyone want to measure subtalar joint ROM for? (the measurements has been well shown to be unreliable anyway; we have no idea what the normal ROM is; at the end of the day, they either have adequate or inadequate ROM for their activity ... why measure it? - what do you actually do with the number?)
    I do not know why they ask you for all that, as they do nothing with that information!

    You need to come to a Boot Camp...
  18. With you there. It ain't all wine and roses over here either!

    I can't help but feel the trailblazers who have advanced the knowledge have left a good portion of the profession behind! There seems to be a big gap.

    Quite true. But this chills me to the core when you consider the implications. The thought process of assessment is being driven by a manufacturing variable of a lab. More, it scares me because the vested interest of the lab is to reduce biomechanics to a series of "measurable" variables and get involved in the teaching thereof. Saves people having to think, gives them confidence. Ultimately a generation of pods is born who think that biomechanics is a process of tractographs and maths and let the actual pathology go hang! And of course if the manufacturing element is lost from the undergrad sylabus they DEPEND on the labs because they don't know the process between prescription/ cast and orthotics:bang:

    Lawrence correctly cited in another thread that what we tend to think of as "rootian biomechanics" is not entirely based in the teaching of Root. Who knows, perhaps that is the reason the "Rootian biomechanics" has become bastardized with something else, driven by lab-which-shall-not-be-named-which-rhymes-with-hanger. To make it accessible to the paying masses of podiatrists.

    Perhaps its merely a dark mood brought on by a week long cluster headache but I sometimes feel the future of biomechanics is not so bright. And I wonder if that is by accident or dark design. For every colleague I meet who trys to grasp biomechanics (at whatever stage in their journey they are) I meet so many more who just can't be bothered.

    Enough conspiracy theory.

  19. Lawrence Bevan

    Lawrence Bevan Active Member

    Nothing like a bit of self-promotion:D

    I did the Boot camp - liked the 1st day.

    How do you know the ROM is "adequate" without assessing it? Maybe its inadequate and that's the source of their pain.

    Measurement of STJ ROM by measuring heel bisection was shown to be reliable in 1 study I believe - forget the ref - about 6/7 yrs ago in JAPMA. I think they used a caliper to aid the bisection marking. However that's of course only one study. Maybe there is a better way of assessing the ROM other than by heel bisection and observing frontal plane movement?

    Simon, Kevin why havent you produce a version of your "talus tracker" for the mass market??????
  20. Pod on sea

    Pod on sea Active Member

    Yes please! When/where in the UK?
  21. efuller

    efuller MVP

    The labs put it there because it makes them look precise and scientific. It also makes you feel better about using that lab because you used those numbers in school. You are the expert. You should know what should change in the orthotic with different numbers. That is unless no one ever told you in school. I would guess that a vast majority of students and practicing podiatrists could not come up with a explanation of why NCSP is important. I don't recall ever being taught to do anything with NCSP.

    You could ask the labs what they do with the numbers. Does it change how they make the piece of plastic? If they do change how they make the orthotic based on RCSP and NCSP do they have any studies to back up that it improves the othotic. Heck, do they even have any clinical experience where they've given someone an orthotic made one way and then give them an orhtotic made a different way?


    Eric Fuller
  22. Craig Payne

    Craig Payne Moderator

    Of cpourse I assess it! I just do not "measure it and I have no idea why the lab want that info for (...well actually I do know and Eric mentioned the reason above!). Here is what I wrote elsewhere on the STJ ROM:
    No dates for 2010 yet, but it will be listed here and there will be some adverts on Podiatry Arena.
  23. Lawrence Bevan

    Lawrence Bevan Active Member

    What's your assessment method Craig?
  24. Craig Payne

    Craig Payne Moderator

    Nothing special, invert and evert the STJ; observe the ROM; no lines; no measurement tools; is it adequate or inadequate for their activity.
  25. Lawrence Bevan

    Lawrence Bevan Active Member

    you notate it as "adequate" or "inadequate"?
  26. Craig Payne

    Craig Payne Moderator

    Yes; or sufficient or insufficient; but it is always contextualised to their activity type and need (eg sport or occupation)
  27. Lawrence Bevan

    Lawrence Bevan Active Member

    :D Got any data on your reliabilty? :D:boxing:
  28. Craig Payne

    Craig Payne Moderator

    No. Got any on yours? :boxing:
  29. Stanley

    Stanley Well-Known Member

    Why don't you just measure it?


  30. Or indeed why meaure it?:rolleyes:

    I did my undergrad project on intra and inter reliability of measuring RSCP. Been done far better by others using experianced clinicians, my sample group was final year students. The range was 17 degrees for inter-tester!

  31. Pod on sea

    Pod on sea Active Member

    Often STJ motion will be more than adequate (i.e. excessive). If you don't use any measurement, how do you decide how much rearfoot posting to use on your orthotic to control the excessive movement.
    Recently an osteopath colleague of mine added a rearfoot post of 20 degrees varus to an orthotic.He said he tested this with applied kinesiology and the patient 'strengthened' up. In my opinion in put her calc into an extremely inverted position, likely to cause lateral instability. He didn't actually measure anything...but it didn't look good when the patient stood on the orthoses.
  32. Craig Payne

    Craig Payne Moderator

    Since when is excessive movement a problem? Movement and angles doen't hurt and doen't damage tissues. I decide on how much rearfoot posting/wedging based on the forces needed.
    I do that often
    Snake oil. See this thread: Applied kinesiology and foot orthotics: True or scam?
    The evidence that this does not happen. A very few will invert 20 degrees; most won't. Some people will even pronate/evert more when you put them on an inverted 20 wedge/post (and they get better too!)
    Only if supination resistance is low.
  33. Pod on sea

    Pod on sea Active Member

    I want to understand this, and wonder if I am being a bit dense/stuck in the 20th century. As force has magnitude and direction, isn't excessive movement an issue ? Do you measure/observe the change your posting is making to the forces by dynamic pressure scan/video/eyeballing/ before you issue an orthotic?
  34. Griff

    Griff Moderator

    Hi Pod on Sea,

    Force causes movement, not the other way around. Force starts something moving, changes its direction and stops it moving. (See Newtons First Law...)

    Excessive movement is not an issue -> its the forces behind it which may (or may not) be pathological.

  35. Pod on sea

    Pod on sea Active Member

    Hi Ian
    Yes, movement is a visible sign of the effect of the force.
    So how do you apply this therapeutically...are you basically countering one force with another in order to reduce tissue stress, and do you quantify the forces required to do this i.e. how do you translate that into posting/balancing/raises etc. Is it by eyeballing/experience/guesswork/measurement?
  36. [​IMG]

    Just as an aside, measuring IS eyeballing and guesswork. You eyeball and palpate to draw your calc / calf bisections then eyeball the goniometer against your eyeballed lines. But don't let the accuracy of the goniometer fool you, its only as good as the accuracy of you're lines and they are based on eyeballing and palpation. Which has been shown to be unrepeatable.

    Its not measurement OR observation. Measurement is based on observation.

    We now return you to your debate.

  37. Griff

    Griff Moderator

    Hi Pod on Sea,

    Some inevitable familiarities cropping up between this and the 'do you measure...' thread.

    Therapeutically I try to ascertain how much force I need the orthoses to exert in order to bring about a therapeutic effect (reduce the pathological force within the injured structure).

    So taking tibialis posterior tendinopathy as an example, rather than 'measuring' a RCSP of 4 degrees everted and giving a 4 degree varus rearfoot post (in the belief that will 'correct/balance' the foot??) instead the two main things of consideration here (in my opinion) would be the supination resistance test (how much force is required to supinate the foot) and the transverse plane location of the STJ axis (in order to know the available 'area' where the ORF will have a supinatory effect). The posting is dictated by how hard the foot is to supinate. Harder it is -> higher the post.

    So to answer your question, its a bit of guess-timation based on experience and good clinical reasoning.

  38. Pod on sea

    Pod on sea Active Member

    That's a very useful answer..........it's easy to get bogged down in the arguments but at the end of the day it's how we apply it to clinical practice that is important.
  39. Lawrence Bevan

    Lawrence Bevan Active Member

    Actually I dont anyone ever said a 4 degree everted RCSP needed a 4 degree varus rearfoot post. I think Blake said 10 degrees of inversion in the orthotic provided 1 degree of "correction" so according to him your patient would get a 40 degree inverted device.

    Just for a laugh. Once you have decided that a supination resistance test says high force required and the location of the axis is medial and youve decided to use a medial wedge, how do you decide how much?

  40. Ian:

    I don't want to be nitpicky, but I have seen these phrases bantered about on Podiatry Arena for some time and want to make a clarification. To say that "force causes movement, not the other way around" is not exactly correct. A change in force acting on an object will produce an acceleration of that object, unless there is an equal and opposite force also acting simultaneously on that object. The movement of an object can certainly produce force if the movement of the object is decelerated by another object.

    In addition, since excessive movement implies increased strains on tissues, which, by definition, will also include increased tensile stress on the viscoelastic tissues that restrain that movement, then excessive movement, or lack of movement, may certainly be one criteria we use when evaluating what the possible cause of an injury is.

    I would rather rephrase your last sentence as: "Excessive motion is not always the cause of injury but rather the internal forces, moments and stresses that result from that excessive motion that are the cause of injury."

    Hope this makes sense so that the others following along understand these ideas with improved clarity.

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