Imprecise biomechanical terms

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Hypermobility was the obvious incorrect term (thanks Prof Kirby).

'Sagittal (or frontal or transverse(coronal)) plane joint power' just came across in Richard Baker's (thanks Mr Griffiths) website; as 'joint power' like 'power' is a scalar quantity so no components for both

What's the others for bx 'newbies' like myself to avoid / made aware of, mark

on a different topic; was diagnosed with PTSD yesterday by the psychologist, my wife also; makes sense, can explain a lot; supposed to talk about it, so i am ......

 

You've probably noticed (via this forum) that the term "over pronation" is one commonly phrased term which is not biomechanically sufficient to use (i.e. ambiguous, subjective; correlation to pathology "imprecise" in relation/comparison to types of forces present/generated etc...).

Anyway, there's a number of such terms... probably good to develop a list of such terms to be wary of when articulating biomechanical concepts.

More importantly (on the bigger scale of things i.e. wellbeing/life); the following sounds serious (or potentially so)... it sounds like you & your wife need a break... time away from society maybe... or at least in a different place, where the environment is different & more relaxed (to recharge the batteries so to speak). Take an adventure (explore) somewhere different for example.

Whilst learning is good (& I've seen you ask many questions of late)... I'm not sure this topic (biomechanics related) will effectively reduce anxiety issues (levels) to a clinically conducive level. You don't have "PTSD" over biomechanics (or Podiatry) do you?

 

thanks Matt, 'overpronation' yes one that gets 'under the (pundits) skin' for sure

and thanks for your thoughts on the PTSD. I was thinking i'm overdoing the questions a tad, and certainly will give the posts a miss; still enjoying perusing the twitter world and finding some interesting blogs, might restrict to going back to the basics and starting again, there's just so much; but seems to be a lot of journal articles not worth wasting time on also
no the PTSD is not related to podiatric-related biomechanics but again you're right; apparently, which makes sense, it's mainly from a medically stressful last 18/12, 2/12 in bed with b/gouty knees due to a pharmacists dosage error (had them drained 3 times); then i had two pancreatic cancer 'scares' where they couldn't dx due to they couldn't give me the contrast for the CAT scans and NMRI's weren't sufficiently able to dx either, they had to wait 2/12 until the pancreatic lesions 'ripened' before they could endocscopic U/S and biopsy, they drained the 'pseudocyst' (20x30x40mm) which stopped the twice weekly rushed midnight trips to ED for iv morphine, but i've still got IPMN's (the second scare) which finally been 'cleared' but they're still monitoring but being cleared that allowed me to have my renal transplant (13/52 ago). so my dear poor wife has been fretting and nursing me for that time and i've had the rest .... also the psychologist maintains a psychologically traumatic event 40 years ago where, working as a operating theatre orderly and scout nurse in a private 'termination' hospital i had to put a 31/52 foetus into the incinerator 'out the back', still bawl when i talk about that one, so ok they told me to talk so i hope i haven't bored you too much but thanks for replying with your thoughts, and yes 'overpronation' like 'hypermobility' right at the top of the list methinks, all the best, mark

 

Mark your questions and threads have been brilliant tbh . we don?t get much biomechanical chats going on these days on PA. So if you feel up for it continue I will add my 2 cents where and when I can.

Metatarsalgia Shin splints etc are poor diagnosis terms anything that is unspecific in it nature

Even just using the term pronation without saying which joint

PS heal up mate both body and mind - sending best wishes from over here

 

I will throw in 'midtarsal joint locking'! It is now referred to stiffness of the joint tissues.

 

A little biomechanics can be a good distraction from what stresses you.

I'm not so sure that the criticism of joint power is valid. Power = joint moment x angular velocity. Moment is three dimensional concept, that can be broken into components within a single plane. If you had the value of moment in a single plane and multiplied that by the angular velocity in that plane, you would get the power for the movement in that plane. This value might be different than the value of total power in all three planes. I'm not sure, but this makes sense to me. David Winter had two separate papers, one on sagittal plane power of walking and the other on transverse plane power of walking. I'll have to look up Richard Baker's cite and see what he says.

Eric

 

From Richard Bakers website

I think that using separate planes of power can make sense when looking at joints. Different muscles can affect different planes of motion of a joint. At the hip a muscle could be adding power in the sagittal plane and a different muscle could be absorbing energy (decreasing power) in the transverse plane. That is how you could explain the observation of one plane having greater power than the total joint power.

What you think?
Eric

 

Thanks Mark for your post. I thought the PTSD could have been related to issues more traumatic than Podiatry related ones (that's not to say that Podiatry related issues can't be traumatic )... I just didn't want to pry into circumstances associated with PTSD. It takes a lot of courage to express such issues & more so to address & subsequently heal from them. By your account you have had multiple frontal lobe (brain) hits... too many such hits (stress events) will exhaust one's threshold to the point of (emotional/psychological) breakdown (similar to tissue injury threshold limits found within pathological biomechanics). Having various physical (serious medical issues) stressors as well as a deep seated psychological (traumatic emotional event) stressor is enough to tip most humans over the threshold & subsequent state of PTSD (the brain is amazing, albeit puzzling at the same time). All the best in the healing process... & if that in part requires you to tackle biomechanical concepts, then doing so via this forum can be productive. However, if you're able to take a trip somewhere... say in nature (not wanting to sound "new agie"), then that usually helps as well (i.e. cold Canberra to warm North Queensland)... animals can help also. There is also a nutritional element which can help (i.e. increasing good quality omega-3 in the diet, in either food or supplement form).

Being that biomechanics incorporates the study/assessment of living creatures & movement, it is conducive to know & understand correct/appropriate anatomical & physics names/terminology. Particularly when attempting to describe the function of particular structures in motion & the subsequent forces potentially associated with the pathology one is requiring to address i.e. STJ or MTJ position/motion in relation to associated forces directed to the likes of tissues such as Tib. Post., Peroneals, Plantar fascia etc... Having a grasp of this also helps one understand the role of orthotics & subsequent fabrication of them... & tweaking them if need be if symptoms persist (i.e. changing stiffness of device, adding a varus or valgus wedge etc...). Also it helps in articulating such concepts, observation/analysis effectively without running the risk of ambiguity & vagueness along with potential confusion. Now, with that said, I will attempt to elaborate further without messing up terminology & contributing to confusion o)...

In the example of "over pronation" (often used in the context of a prime causal agent in injuries - particularly within the running shoe retail industry); not only should we know why it is an "imprecise biomechanical term" but have a more precise way in describing the intended meaning to correlate what is more accurately at play. For example, "over pronation" really just describes (somewhat) the position &/or motion (kinematics) of the structure (i.e. STJ) & that the position &/or motion (kinematics) has little correlation to the actual cause of injury/tissue damage (I suppose one could say there is an association, more so in some than others, but it seems to be a weak association on the whole). However, forces (kinetics) plays a far more consistent (empirical) correlative cause in the role of injury/tissue damage. Hence we should be focussing more attention on reducing forces (addressing kinetics) which are assumed to be causal to tissue breakdown... as opposed to the posture/motion (kinematics) of the foot.

One way to help assess such forces (albeit, in a static environment; hence doesn't assess the greater forces associated with dynamic activities) between foot to foot & individual to individual is an in-clinic test such as the "supination resistance test" (coined by Prof. Kirby). This test provides the clinician a gauge of an estimated degree of force required to resupinate the individual foot from its relative pronated position to a relative position which is neither pronated nor supinated (via placing a dorsal/upward force under Talonavicular joint)... & subsequently can be used as a gauge for determining what is required to reduce the forces associated with this element of motion/movement (pronation or supination) present with the individual. If there requires a large degree of supination moment (dorsal pressure at Talonavicular joint via supination resistance test) to resupinate the foot (which would be described as high supination resistance force), the clinician may deem this as a potential causal agent for the likes of such injuries like Tib. Post. strain (MTSS), Plantar fasciitis etc... It can also be reflective of the (transverse plane) axis of the STJ (i.e. medial deviated STJ axis)... of which such feedback can then go into the decisions for the fabrication of orthosis (i.e. stiffer materials, medial heel skive, medial flare etc... to provide sufficient supinatory moments to dampen pathological forces). Conversely, if the clinician is able to resupinate (or just supinate) the foot with little effort (which would be described as low supination resistance force) then this may potentially correlate to stress/injury to the supinators of the foot i.e. the Peroneals. This feedback can also be reflective of a lateral deviated STJ axis & thus the need to provide sufficient pronatory moment elements within orthosis fabrication i.e. lateral heel skive, valgus wedge etc...

Thus the reason the term "over pronation" is insufficient is because there are some individuals who may be deemed "over pronators" (i.e. have poor foot posture index) yet may not have a high supination resistance force test result (less force needed to resupinate the foot) & thus have few injuries; whilst other individuals who have a better foot posture index (less pronated posture) may exhibit greater supination resistance force (greater force needed to resupinate the foot) & have potential greater chance of injuries; hence posture/motion (kinematics) not an accurate predictive indicator compared to forces (kinetics) at play. Whilst those individuals who resulted with a high supination resistance force test (regardless of foot posture/motion) showed a more consistent predictive indicator of higher rates of pathology/injury... conversely, those individuals who resulted with a lower supination resistance force test (regardless of foot posture/motion) showed a more predictive indicator of lower rates of pathology/injury (putting aside too low supination resistance force test which may reflect the likes of Peroneal stress/tenosynovitis).

Now, I hope I've explained above with sufficient biomechanical terminology, reducing the risk of confusion. With the above said, a phrase keeps popping in my head... "structure governs function"... at what degree of truth is this statement?

 

Hi Mark

Sweet Fanny Arkwright to do with biomech. but England are all over Sri Lanka at the moment. Warming up for the Ashes but I fear that Aussie will still cream us. Now there's stress - for us the post traumatic will come after the creaming!

Keep lifting the tinnies

Bill

 

Mark:

This is a good topic for Podiatry Arena.

The term hypermobility is one that simply doesn't make sense in the modern biomechanical era. Hypermobility should be replaced with the term decreased stiffness or increased compliance to more accurately reflect the load versus deformation characteristics of the clinical meaning of hypermobility (Kirby KA, Roukis TS: Precise naming aids dorsiflexion stiffness diagnosis. Biomechanics, 12 (7): 55-62, 2005).

The term overpronation is a difficult one also since pronation is a term describing the triplanar motion of the subtalar joint (STJ) and maximally pronated should be as pronated as any STJ can rotate to. However, the authors who have complained of the term overpronation need to come up with an alternative term to describe the foot that has an overly everted calcaneus, an overly plantarflexed talus and excessive flattening of the medial longitudinal arch, which are all common structural changes seen in the feet that are commonly said to have overpronation and more commonly called a pes plano valgus deformity. Unless these authors who complain of the term overpronation can come up with better replacement term to describe the structural characteristics which are obvious in pes plano valgus deformities, then no progress in terminology will be made.

I suggest using a classification (i.e. Grade I, II, III) of medial deviation of the STJ axis to describe the spatial orientations of the talus relative to the calcaneus and developing a new measurement parameter which describes the structural angle of the medial longitudinal arch to replace the term overpronation in patients with pes plano valgus deformity. This would certainly be a step forward since STJ axis spatial location and medial longitudinal arch angle are independent variables and would both be needed to better describe the structural characteristics of pes plano valgus deformities.

Good discussion.:drinks

 

Speaking of messing up with terminology... I messed up above (underlined section)... & I can't edit it now . The text should read... "pronators of the foot i.e. the Peroneals"... & not "supinators" (must of had too much supination on my mind - well, that's my reasoning )

I think there are two reasons why the term "over pronation" is inadequate... or inadequately used - 1. being the term used to describe the causal agent of injury (what I focussed on); 2. being the term used to describe the posture of the foot or spatial location of the STJ axis or Talus orientation (what Kevin has highlighted above). I think there is adequate terminology & reasoning present to address the causal of injury reasoning i.e. forces/velocity being the prime cause - not kinematics. However, the posture reasoning is a bit more difficult (as Kevin highlighted). I sometimes use the term ("over pronation") to describe the concept involved (foot everting too much & for too long in gait cycle) to my patients... they have a better chance of understanding the concept without having to grasp further more foreign concepts such as Subtalar Joint, Talus & the medial deviation thereof. Yet, in a biomechanical/Podiatry setting I can see this is inadequate due to vagueness & subjectivity. The following suggestion certainly reduces the element of vagueness but there is still is an element of subjectivity... i.e. what determines the grades of I, II & III. Thinking out loud, possibly measuring the degree of Navicular or Talonavicular medial deviation from the individual's neutral (neither pronated or supinated position) compared to their resting stance may be of use... yet, this is a variable factor based on foot size... hence maybe a ratio could be obtained with this element in mind (???). Then again, maybe measuring such (getting a precise status) isn't all that important as usually such cases are visually obvious on what needs to be done (at least in a clinic setting).

The following may not address all the variables adequately... but if a "measurement parameter" is required for a more reliable classification system... maybe using one of those bendable rulers (i.e. Flexible Curve Ruler, see below) which holds it shape (may be of use)... hence you compare the medial contour with the foot in "neutral" to that of "relaxed stance"... note the difference & measure... to then obtain a score based on a grading system around the size of foot & medial deviation of Navicular/Talonavicular joint... & maybe call it Navicular Deviation Ratio (NDR). Just an idea... haven't thought of this until now.

 

Origin and insertion; should be proximal and distal attachments

 

'locked' as in STJ position; just watched https://www.youtube.com/watch?v=8hUWVYikBaQ

should it not be 'maximally supinated', or 'position of maximum stiffness'