Foot orthoses outcomes and kinematic changes

[Craig Payne]

1. We all use various types of foot orthoses in clinical practice in an attempt to alter the pattern of rearfoot motion to "improve" biomechanics and make patients better.
2. Numerous outcomes studies, patient satisfaction surveys (many with methodological flaws) and RCT's show patient do get better with foot orthoses that attempt to alter the pattern of rearfoot motion.
3. The numerous kinematic studies (many with methodological flaws) are about evenly divided as to if foot orthoses do actually alter the pattern of rearfoot motion or not. Half show no differences in rearfoot kinematics and the other half show such small (but statistically significant) differences that the biological significance of those differences need to be questioned.

Does anyone see the paradox here? :confused: What we do clinically works, but not by trying to do what we think we are doing :confused: (... as I tell the students - I used to know what I was doing)

In an attempt to resolve this paradox, one of our projects this year measured patient symptoms (FHSQ) at issue of foot orthoses and at 4 weeks follow up. At issue of foot orthoses, rearfoot kinematics was also measured with and without the use of the foot orthoses. Guess what we found? ---- there was no correlation between changes in the pattern of rearfoot motion and symptom reduction :confused:

This is troubling as I have spent most of my professional life trying to alter patient's pattern of rearfoot motion .... they get better, but not because of the changes in rearfoot motion :rolleyes:

What say you?

[Ian Linane]

Hi Craig

Forgive naive in put but does the following perhaps contribute to the debate.

1. Ultimately, the human body / mind knows what it needs to maintain
stability in motion and any attempt to bring physiological forces that
enable it to move towards what it needs are readily seized by the body /
mind. This is a holistic approach that I supect we greatly undervalue in
our reductionist methods of medicine.

2. The applied forces to the rear foot succeed (if that is the word) not so
much by changing the pattern of rear foot action but by the aquired
changes in the mid and forefoot resulting from change in rear foot position.

3. Rear foot action is very much about intial contact and I wonder if it is a
point when mechano receptors in the muscles are least active overall
(someone who knows this stuff can happyily correct me).

4. Perhaps, the altered midfoot position at ground contact feed
long lost proproceptive information through hitherto limited (due to lack
of stimulation via overpronation) feed back mechanoreceptors and, even
milliseconds prior to early heel lift, the forefoot signals are responded
to more quickly. (Within the little bit of treatment I do for mind issues we
speak of an atavistic state, a throw back to primitive processes.
Perhaps the change in rearfoot, its consequences upon mid and forefoot
mechanoreceptors begins to generate a healthy throw back into mind
memory of how our limbs should be working.

5. Where the full effectiveness of this may fall down is at the point in heel
lift where the mid foot is most vulnerable to MTJ in roll because it does
not have an undulating surface to walk on.
(Do the cases where rear foot control seemed less effective reveal if the
midfoot inrolled on these people more?)

Just some ideas. They may be crap but hopefully I can at least write reasonable crap if not good biomechanics. :D

cheers
Ian

Ps. Craig, did you get email regarding your university having image resources
of body posture

[Craig Payne]

I am not so sure its proprioception/sensory input - we have now done several post tib nerve block studies and ice studies (to numb plantar surface) and studies using 40grit sandpaper on top of orthoses (to increase sensory input) - in all studies alterations in sensory conditions/input did not alter the kinematic response to the foot orthoses ...... several studies by others have shown the importance of plantar sensation to balance and stability, which we are not investigating. We were concerned about, do you have to feel a foot orthoses (ie sensory input) to respond kinematically to it? - the answer so far is NO.

At the end of the day, we use foot orthoses to alter foot function to get symptomatic relief. We have measured a whole battery of kinematic, kinetic, EMG and pressure parameters/variables in several studies to see what ones foot orthoses do actually alter and MOST IMPORTANTLY, which of the parameters/variables are related to a reduction in patient symptoms (plantar fasciitis and patellofemoral pain sydrome are the two populations we are using) - the main study (above) showed it wasn't reafoot motion changes that are related. We think we have narrowed it done to just one functional parameter (or maybe 3) that foot orthoses do alter that is related to symptomatic relief. We just not yet ready to 'sing and dance' about it yet until we finish 2 RCT's next year testing it and look at the validity/reliability of clinical tests associated with it.... watch this space :eek:

[Ian Linane]

I'll keep watching! :cool:

As you feel to have a inkling already do you think my suggestions are way of beam?

Ian

[davidh]

Hi chaps,
Rearfoot control to control the rest of the foot was how I was taught biomech many moons ago. I was taught (like many others) that a rearfoot post tilted the calcaneus (in some way) and this influenced the position of the foot in midstance and therefore toeoff.

However, after working with a vertical loading gait analysis system for a few years (Musgrave) I began to realise that the vast majority of my patients simply didn't load anywhere near full bodyweight until they had finished heelstrike and were in the first half of midstance.
Was the load at heelstrike enough to "tilt" the calcaneus?
What seemed much more likely to me was that the medial heel correction was simply acting as a stabiliser for the expensive "arch supports" I was fitting :eek: .
I still subscribe to this.
Regards,
David

[Craig Payne]

Rearfoot control to control the rest of the foot was how I was taught biomech many moons ago.I have been doing that for years and teaching it for years ---- IT WORKS -> patients actually get better when doing it (the evidence shows that they get better). But the evidence is also clear, that when we try to do it, it dosen't actually happen, but the patient still gets better .... don't figure :confused: .... remind me in 6 months to come back to this thread with what I hope is the answer with the evidence.

[davidh]

But the evidence is also clear, that when we try to do it, it dosen't actually happen, but the patient still gets better .... don't figure :confused: .... remind me in 6 months to come back to this thread with what I hope is the answer with the evidence.

Here I go with a "conjecture-vs-science" comment :) .
I found my patients got better too, but I suspect not for the reasons I was taught.

Nowadays, by using mostly small (2 degree) FF posting only for the majority of my patients they still get better. I notice that they respond as fast but with not so much of the acclimatising problems I used to have with 4-degree rearfoot posts. Devices can be smaller too :) .
I still use heel-lifts as needed.

As an aside to that, in conjunction with a colleague and a well-known USA lab, this summer we developed a casted device which can be used in a soccer boot. Professional players in the UK (and guys from outside the UK but who play for UK clubs) pretty much all wear their boots anywhere from one to three sizes too small. Hence there's a problem getting a rearfoot-posted device into the boot along with the foot. The FF-posted soccer orthoses are currently used by some of the players from two Premiership Division clubs - they're comfortable straight away, the player can still wear his boots too small, and they seem to be working :D !

Look forward to your research findings Craig.
Cheers,
David

[pgcarter]

I would venture to suggest that it is not always rear foot motion patterns that are indicative of symptoms anyway....this was Roots idea though. I like the idea put forward by the English guys about forefoot controlling rear foot through muscular responses to pressure changes under foot. Not sure I'm really saying it the way they did....but I think in practice I'm much more concerned with forefoot/first met shaft position and timing/success of hallux dorsiflexion than I am with rear foot position.
I think I see many feet that have trouble that hardly move in the frontal plane at all but are excessive pronators at STJ....I don't try to change the rear foot motion....I try to change first ray function.....which is really about the forefoot and its relationship to the ground.....which of course has a BACKWARD REACHING? influence on the rear foot.
How's that for holistic groping in the dark?
Regards Phill

[Ian Linane]

I knew Australian Podiatry courses were more interesting than English ones. "Groping in the dark" never appeared on our curriculum. :(
If I stay posting on this site long enough can I do an MSc in it? :D

Ian

[Sean Millar]

In my limited clinical experinece rearfoot position influences 1st ray function. This is particularly apparent in Functional hallux limitus. the 1st phalanx has limited dorsiflexion on the 1st met. in rcsp, however this usually improves significantly in ncsp. Which lends support to the arguement that the reafoot position, may be influencing structures more distally. Following on from this, I usually find when the client stands on a functional orthotic, the 1st phalanx dorsiflexion is greater than when the orthotic is not in place. The large assumption is the relates to dynamic gait :confused:

[Craig Payne]

In my limited clinical experinece rearfoot position influences 1st ray function
There are two publications that support this - BUT, we pretty sure its not really changes in rearfoot position/motion that influences the first ray motion. We pretty sure it changes in the rearfoot kinetics (ie forces) that influence first ray function. We can easily get changes in first ray function by influencing rearfoot forces without actually changing rearfoot position or motion (kinematics). Its just when you do manage to change rearfoot position, you also change the forces. BUT, you can change the forces without changing the position..... here in lies the answer (and don't forget its kinetics (ie forces) that damage the tissues and not motion or position (ie kinematics). Symptoms get reduced only when the forces in the tissues are reduced.

[Sean Millar]

The last australiasian conference started to bring these issues the arena. but from a practical issues. how do we measure the kinematics in a clinical situation?. is it something we could include in our daily practice? the possibility of being able measure our infleunece on the foot more quantatatively is very exciting. :cool:

[Craig Payne]

I don't want to say too much until we are more sure we are right. But we testing validity and reliability of a couple of static clinical tests with and without patient standing on foot orthoses to predict the kinetic changes dynamically ....watch this space.

[pgcarter]

Iain,
In view of current work place political correctness, I can assure you the lights are always on....and there is no groping...as interesting as it sounds, but I regularly urge my students to cop a feel of as many feet as they can get their hands on....all good experience for clinical practice.
On a more serious note I do have trouble in early second year getting them to actually touch each other (on the feet) in my classes to begin to get a good broad base line "feel" for feet.
Regards Phill Carter

[Robert D. Phillips, DPM]

Hello Craig,

I enjoyed your comments about orthotics not highly affecting the kinematics, yet providing invaluable aid of symptoms. :eek:

Just a few comments to back you up in your observations, yet I'm sure you've discussed these possibilities with your students many times.

1) Interestingly, Root maintained that you only have to control the last 1 degree of pronation (or maybe less) to have complete resolution of symptoms. He maintained that pronated feet are not usually symptomatic, only subluxed feet. So you need very little change in kinematics to feel marked relief of symptoms

2) I think Irene McClay did a nice job with the Blake orthotic study to show that it was the kinetics, not the kinematics that was so drastically changed.

3) I believe that many of the changes are not in the rearfoot to ground, but in the forefoot to ground and the forefoot to rearfoot kinematics, especially in the intercuneiform relationships. Haven't figured out the best way to measure these.

4) Most of the studies do not utilize each subject as their own control, but instead give averages for a large variety of foot types. For example, it would be interesting to see what happens only in those type of feet that are judged to have 5-10 degrees of forefoot varus with all other parameters nearly normal. Good luck trying to find such a population that is large enough to study.

So with those small observations, it would be interesting to try to understand the real reasons for so many of treatment modalities working, but the problem is that no one wants to develop their education background necessary to understand the real reasons.

With a politically correct happy holidays to everyone. best wishes for the new year, :)
Daryl Phillips

[Ian Linane]

"We were concerned about, do you have to feel a foot orthoses (ie sensory input) to respond kinematically to it? - the answer so far is NO."


Hi Craig.

Something I wanted to note a while ago in response to the above. Where we feel orthoses is significant and I wonder if the assessment of the numbed lower limb took into account the downward feed of information:

A person may not feel the affect of the orthosis in the numbed foot / leg but the change in centre of gravity in gait and position of other aspects of the body may be feeding the body / mind scenario. Surely feed back is not simply oneway. A minor change in position of the trunk (resulting from the unfelt-foot- but mechanical reality of changed position) would, I am assuming, cause muscular reaction in a downward direction.
Would this be sufficient?

Cheers
Ian

[Craig Payne]

Would this be sufficient?

Not sure - we just starting to get into this. We are looking at doing some work on "leg stiffness" (the biomechaical defnition of stifness) and the influence of that at heel contact on the parameters that we want foot orthoses to influence - ie the influence of these proximal factors, of which this is just one.

[Craig Payne]

Daryl
Good to hear from you.
With a politically correct happy holidays to everyone. best wishes for the new yearhttp://www.podiatry-arena.com/images/offtopic.gif
I know this off-topic, but I have been watching Fox News lately (...yes I know its more to the right), but I can't get over some of what I am seeng:
* baning of nativity scenes by some government agencies
* christmas not being celebrated by some schools
* all the litigation surrounding the political correctness of christmas
* a teacher allegedly suspended for talking about god in the context of the declaration of independance...

Talk about political correctness gone nuts!http://www.podiatry-arena.com/images/bonk.gif

I do enjoy the Bill "no spin zone" O'Rielly show - mainly cause he drives liberals nuts! and I love the way they go back at him :eek: - but, did you read this critics attack on O'Reilly's stand on Christmas Under Seige (http://www.newshounds.us/2004/12/15/christmas_under_seige.php) ?

Also, this from WorldNetDaily (http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=25758):

In Seattle, a King County executive named Ron Sims sent out a memo to county employees asking them not to say "Merry Christmas" and to be "religion neutral." Sims was mocked and scorned even in that permissive city. The memo was filed under "stunningly foolish."

The Wisconsin Municipal Clerks Association ordered religious ornaments banned for the state "holiday" tree.

A Frederick County, Md., school employee was prohibited from handing out Christmas cards on a public-school campus.

Santa Claus was banned by the Kensington, Md., town council because of two complaints that ol' Saint Nick would offend some citizens at a tree-lighting ceremony. Santa showed up anyway, presumably with his lawyer – an elf named "Swifty."

Red poinsettias were banned from the Ramsey Court House in St. Paul, Minn., because they offended one person who believes the flowers to be a symbol of Christianity.

Elementary school principal Sandy Niemiera announced to startled Plainfield, Ill., students that all holiday celebrations would be banned because of "diversity" concerns.

And in Maine, one school district has banned Christmas trees because some cultures don't believe in them.
God bless the USA :)

[Ian Linane]

Thanks for the reply Craig. Found the Fox articles and responses fascinating.

I was in disussion with a physio colleage of mine who, like me, also is involved in holist approaches to treatments. We discussed proprioceptive responses and he reminded me of the holistic principle of "less equals more"
i.e. a little lets the body do a lot but that the more we do the less the
body can do.

I paste below his comment:

"One thing that comes up over and over again in Holistic Medicine is "Less = More!".

I am very ill equipped to argue biomechanics with you or any of the very esteemed contributors to this debate but I suggest that the tests for proprioception were too 'heavy handed'.
Remember the fable of the Princess and the Pea?

Where zero interference = maximum allowance for holistic accommodation to external forces and 100% interference = total opposition reflex then, I suggest that the nearer one gets to zero stimulation, the greater the automatic proprioceptive adjustment.

(e.g. I have just discharged a patient who presented with G.minimus spasm. He failed to respond well to either ultrasound or interferential therapy and was unable to tolerate deep petrissage. Bea reminded me of the "Less = More" philosophy and as a last resort (and with a great deal of trepidation) I 'tickled his bottom'. The result after 10 mins? Instant relaxation of the muscle which has been sustained with reducing applications of heat over a few days at home.)

Worth a thought?"

Taking into account the previous post where Root was suggested to say that it is the last degre of pronation that was significant

People generally adapt well to significant callous etc but a simple, tiny stone in the shoe generates remarkle alteration of gait. :eek:

Cheers
Ian

[Glenn Z]

G'day Craig
Something that does not seem to have been raised is that the device modifies the timing of motion/loading in pedal joints. Given the complexity of foot function, a small alteration in the timing of the application of a force, irrespective of its magnitude, has the potetnial to allow the structure to more readily accept that force.
Certainly the move to a holistic approach of foot disorder Mx has had demonstrable benefits- i can recall a case presentation of a young athlete with chronic medial tibial stress syndrome- her pedal mechanics appeared to be well controlled with orthoses yet she still had significant pain. When a Physio assessed her, she demonstrated significant low back and pelvic instability. The introduction of a programme aimed at improving her core stability subsequently completely resolved her symptoms- thus perhaps we are still too obsessed with the foot as the root (no pun intended) of all evil when it comes to lower limb pathology. :eek:
Certainly, as has been raised a number of times, we are in (or at least coming to) a position of widely questioning the biomechanical models we studied at uni an hence we are in the process of becoming a true science rather than an art. :D
Glenn

[Kevin Kirby]

Hello Craig,

I enjoyed your comments about orthotics not highly affecting the kinematics, yet providing invaluable aid of symptoms. :eek:

Just a few comments to back you up in your observations, yet I'm sure you've discussed these possibilities with your students many times.

1) Interestingly, Root maintained that you only have to control the last 1 degree of pronation (or maybe less) to have complete resolution of symptoms. He maintained that pronated feet are not usually symptomatic, only subluxed feet. So you need very little change in kinematics to feel marked relief of symptoms

2) I think Irene McClay did a nice job with the Blake orthotic study to show that it was the kinetics, not the kinematics that was so drastically changed.

3) I believe that many of the changes are not in the rearfoot to ground, but in the forefoot to ground and the forefoot to rearfoot kinematics, especially in the intercuneiform relationships. Haven't figured out the best way to measure these.

4) Most of the studies do not utilize each subject as their own control, but instead give averages for a large variety of foot types. For example, it would be interesting to see what happens only in those type of feet that are judged to have 5-10 degrees of forefoot varus with all other parameters nearly normal. Good luck trying to find such a population that is large enough to study.

Daryl Phillips

Daryl, Craig and Others:

Good to see you contributing Daryl. Hope you had a nice Christmas and holiday season.

Mert Root's contributions to our understanding of foot biomechanics is well known. However, to put his comments into a more modern biomechanical perspective, I would say that foot orthoses should apply moments that are in the opposite direction to the pathological moments that are causing the tissue injury or abnormal gait function in the patient. This is more precise than saying "controlling the last degree of pronation". In addition, this forms the basis of how I treat my patients clinically with foot orthoses.

I agree that Irene McClay-Davis and coworkers have done some very fine research regarding the alteration of joint moments with foot orthoses. Anne Mundermann and coworkers' orthosis research also supports Irene's findings.

I also agree that the midfoot and midtarsal joint kinetics are extremely important and I believe that kinetic modelling and finite element modelling will greatly help us understand pathology in this region of the foot.

In regards to developing better research, I think that using only maximally pronated feet with medially deviated subtalar joint (STJ) axes in one group makes more sense that dividing research groups based on "calcaneal position" or "forefoot to rearfoot relationship". Considering the residual pronation moments and sinus tarsi interosseous compression force will be much higher in magnitude in individuals with medially deviated STJ axes, I would think that these individuals would respond much differently to foot orthoses than those feet that have more normal STJ axis spatial location and do not stand in the maximally pronated STJ position.

Thanks for your stimulating comments, Daryl.

[Robert D. Phillips, DPM]

Hello Kevin,

As always, you have some good points to make. I do not disagree with the ideas about moments around the subtalar joint axis. I likewise utilize such thinking in many of my patients.

As I approach the patient, though, my thinking always goes like this: 1) what anatomical structure(s) are painful? 2) What type of mechanism could produce such pain? (i.e. tension, compression, etc.) 3) Why is the mostly likely mechanism occurring? (pronation of the STJ, weakness of the peronei, etc.) 4) What are the goals of the orthotic therapy? The more specific I can identify the goals of therapy, the more likely I am to achieve those goals and have a happy patient.

While orthotics always change moments around at least one joint of the foot (actually any pad or rock in the shoe will change the moments around at least one joint of the foot), sometimes my only goal is a redistribution of pressure. You have probably noted how "rigid" orthotics alleviate pressure under the calcaneal tubercle. Maybe that's all I need to do, and I don't even worry in that case too much about how much the moments around the STJ axis are being changed. Sometimes the orthotic only decreases the plantarflexion moment around the midfoot joints being created by the plantar intrinsic musculature in early propulsion. Again in this case no attention is being paid to the STJ axis moments. As you have probably already noticed, not everyone with heel pain is a pronator, yet orthotic therapy seems to help a great many that seem to have little if any abnormal rearfoot pronation.

My comments about division of feet were intended not to be a precise suggestion, but only to demonstrate how little attention is paid to specific foot types or etiologies of the abnormal pronation or supination in most of the orthotic studies. Usually what we get is a statement like this, "XX number of subjects were chosen. All were healthy with no symptoms in their feet and no history of injury..." There is no indication of what types of feet were examined, whether they looked only at feet with laterally displaced calcanei, medially displaced STJ axes, forefoot varus feet, feet with greater than 20 degrees of frontal plane movement around the MTJ, or any other of a number of proposed foot types. Therefore, with such a broad spectrum of foot types in the study it may not be possible to statistically prove or disprove the hypothesis of the study. The possibility of type 2 errors seems to be much higher than the power studies would predict.

Again thank you for your important comments. :) I'm pretty much in the same track you're in about moments and I appreciate the tremendous work being done by you and the many others out there to put more mechanics into biomechanics.

I trust that you and yours had a great holiday season. I will try to make a few more postings in the future than I have done the past year (if I can get time away from printing so many pictures of the granddaughter - now I know why research productivity decreases after the grandchildren come).

Best of wishes for 2005
Daryl

P.S. - I would like to propose a couple of questions:

1) Is it ever possible to stand with all the plantar muscles of the foot relaxed, and have any of the joints of the midfoot (MTJ, CNJ, MCJ) not dorsiflexed to their end range of motion? If so, where are the plantarflexion moments coming from that would equalize the dorsiflexion moments being placed around these joint by the GRF?

2) With a Kirby skive, is the calcaneal fat pad directly above the skive displaced medially or laterally? How could we prove or disprove any statements about movement of the calcaneal fat pad?

[Kevin Kirby]

Hello Kevin,

As always, you have some good points to make. I do not disagree with the ideas about moments around the subtalar joint axis. I likewise utilize such thinking in many of my patients.

As I approach the patient, though, my thinking always goes like this: 1) what anatomical structure(s) are painful? 2) What type of mechanism could produce such pain? (i.e. tension, compression, etc.) 3) Why is the mostly likely mechanism occurring? (pronation of the STJ, weakness of the peronei, etc.) 4) What are the goals of the orthotic therapy? The more specific I can identify the goals of therapy, the more likely I am to achieve those goals and have a happy patient.

Daryl,

Good to hear about the grandchild being enjoyed by grandfather. My oldest son got married this summer so I'm probably not too far behind...but in no great rush at this time to reach your elder status. :)

Your approach to foot orthosis therapy is identical to the one that Eric Fuller and I are writing about currently in a chapter on Tissue Stress and STJ Rotational Equilibrium. Your paragraph above is almost identical to one of the tables included within the chapter. Seeing that we think nearly identically in this regard pleases me greatly. I greatly respect your knowledge and opinions and have always looked up to you as one of the leaders of biomechanics within podiatriy within the US, even though we have had our share of animated discussions in the past.

I don't have time now to answer your other questions but, when I have time, I will try to get around to doing so. Please give my regards to the family.

[Kevin Kirby]

P.S. - I would like to propose a couple of questions:

1) Is it ever possible to stand with all the plantar muscles of the foot relaxed, and have any of the joints of the midfoot (MTJ, CNJ, MCJ) not dorsiflexed to their end range of motion? If so, where are the plantarflexion moments coming from that would equalize the dorsiflexion moments being placed around these joint by the GRF?

2) With a Kirby skive, is the calcaneal fat pad directly above the skive displaced medially or laterally? How could we prove or disprove any statements about movement of the calcaneal fat pad?

Here are my answers, Daryl.

1) I would imagine that the plantar intrinsic muscles are not necessary to be firing at all times but are probably recruited intermittently to help reduce the tensile loading forces on the plantar ligaments of the midtarsal joint (MTJ) and other midfoot joints. I think that we should not talk about "dorsiflexed to end range of motion" for the joints of the MTJ and midfoot since their position will be very dependent on the prevailing dorsiflexion and plantarflexion moments occuring across them during weightbearing activities. The MTJ and midfoot joints should be thought to be more "springlike" in that they will be able to allow the foot to deform more as there is more dorsiflexion moment applied across these joints by ground reaction force (GRF). Plantarflexion moments for the MTJ and midfoot joints come from plantar ligament tensile forces, plantar intrinsic contractile activity, contractile activity of the peroneus longus, flexor digitorum longus, flexor hallucis longus and posterior tibial muscle and plantar fascial tensile forces.

2) I don't know whether the calcaneal fat pad significantly displaces medially or laterally with the medial heel skive orthosis modification. I would guess that if it does then it is due to prevailing medial-lateral shearing forces acting on the skin that does not also simultaneously affect the calcaneal position on the orthosis plate. I am not so concerned about movement of the calcaneal fat pad but am more concerned about the kinetics of what I am doing and how this will affect the symptoms that my patient has, how comfortable they will be with the orthosis and the patient's overall gait function.

Good questions, Daryl. Have you been doing anything more with Erin's dynamic gait replicator?

[Atlas]

Great thread.

Craig. In view of Gardner's rule, I presume that perhaps most of these symptoms would have been intrinsic to the foot.

On the other hand, if proximal (eg.knee) symptoms were altered without detected changes in rearfoot motion, could therapeutic success be attributed to velocity changes? Was velocity of the rearfoot measured in addition to kinematics? Perhaps timing is a small part of the big picture. Common-sense suggests that musculo-skeletal structures work harder to counter a faster moving entity at the end-point (of movement) alone.

If I was a baseball catcher or wicket-keeper, first my hands would prefer to catch a slower ball. But failing that, my hands would prefer to meet the fast projectile earlier and move my hands back with the ball, and hence decelerate it over the longest period possible. Perhaps this is one way an orthotic becomes therapeutic without making a significant change to total movement. If the last phase of rearfoot motion is decelerated, then the eccentric demand of the rearfoot supinators would decrease, and the velocity of internal leg rotation would decrease. Is this connected to Root's final degree of pronation, as a previous poster raised?


Of course my little theory would be blown up if EMG studies (of the rearfoot pronators) and velocity studies (of the rearfoot motion) were assessed during the same study and were 'unchanged' also; despite symptomatic reduction.

[GarethNZ]

Hi Craig,

I would be interested to know what structures were the ones identified as causing discomfort for the patients involved in you results

What sort of activities were they involved in? Physical activity or mainly sedentary?

I would also be interested in knowing how you did your rearfoot measurements? Were these in static stance or via functional measurements?

We have noticed a similar result, but only for people suffering from Plantar fasciosis. Their rearfoot mechanics (and most other within the foot) have been disregarded and by treating patients pain there has been more confidence put back into our treatment.

regards,

Gareth

[Craig Payne]

I would be interested to know what structures were the ones identified as causing discomfort for the patients involved in you results All had insertional plantar fasciitis. We will soon be repeating the methodology in PFPS to see if the parameters that need to be altered are the same (I don't believe they will be)What sort of activities were they involved in? Physical activity or mainly sedentary?All sorts
I would also be interested in knowing how you did your rearfoot measurements? Were these in static stance or via functional measurements?Dynamic 3D

[Atlas]

Plantar fasciitis/fasciosis, in my clinical experience is invariably assisted (at least short-term) by low-dye taping. What does low-dye taping do to rear-foot kinematics? Other than restrict the range closer to neutral position, probably very little.

What low-dye taping does do, and this perhaps supports Phil's theory, is that is has more of an influence on the mid and forefoot. I envisage that low-dye taping unquestionably removes tension from the plantar fascia structure, without the direct pressure exerted by a device without groove.

Low-dye taping, I envisage also pulls the 1st ray into plantar-flexion; and I assume the other rays...hence reducing tensile stress on FHB.



(Low-dye) taping isn't respected academically, in view of the consensus (I disagree with) that tape slackens in 20 minutes; but design me an orthotic device that does what low-dye taping does, and I will buy it.


Back to the topic now. Craig's study could not detect significant changes in RF motion in effective orthoses for plantar fasciits. This is mirrored clinically, IMO, due to the potent (albeit short-term) effect of low-dye taping on plantar-fasciitis; despite an assumed mild rear-foot influence.

[Craig Payne]

What does low-dye taping do to rear-foot kinematics? Other than restrict the range closer to neutral position, probably very little.

Low dye strapping lowers the force to get the windlass established to about 10-20% ---- massive reduction ---- imagine the forces then going through the plantar fascia with the tape on and the effect of that massive reduction of force through the injured tissue.

[Atlas]

My guess would have been > 10-20%.

But beyond the windless effect (which I presume does not relate to lesser rays), low-dye taping surely influences all rays, all FHB slips, and hence, I again assume, the total tensile stress through the plantar fascia.

[Atlas]

My guess would have been > 10-20%.

But beyond the windless effect (which I presume does not relate to lesser rays), low-dye taping surely influences all rays, all FHB slips, and hence, I again assume, the total tensile stress through the plantar fascia.


Typo. I meant FDB....not FHB.

[Craig Payne]

My guess would have been > 10-20%.
It reduced it by 80-90%, down to 10-20% of the original force - sorry for the confusion.

[Kevin Kirby]

Plantar fasciitis/fasciosis, in my clinical experience is invariably assisted (at least short-term) by low-dye taping. What does low-dye taping do to rear-foot kinematics? Other than restrict the range closer to neutral position, probably very little.

What low-dye taping does do, and this perhaps supports Phil's theory, is that is has more of an influence on the mid and forefoot. I envisage that low-dye taping unquestionably removes tension from the plantar fascia structure, without the direct pressure exerted by a device without groove.

Low-dye taping, I envisage also pulls the 1st ray into plantar-flexion; and I assume the other rays...hence reducing tensile stress on FHB.


As Craig noted in his research, the Low-Dye strapping reduced the tension in the plantar fascia by 80-90% when measuring the force to establish the Windlass Effect of Hicks. This makes sense when you model the foot as I have previously explaining the biomechanical etiology of functional hallux limitus (Kirby, KA: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 139-152).

Low-Dye strapping causes a anteriorly directed force on the plantar calcaneus and a posteriorly directed force on the anterior forefoot. These two forces will cause a rearfoot dorsiflexion moment and a forefoot plantarflexion moment, especially when the strapping is exerting a large tensile force on the skin of the foot (such as when the foot is in the late midstance phase of gait).

Since the plantar fascia, like the Low-Dye strapping, also causes an anteriorly directed force on the plantar calcaneus and a posteriorly directed force on the anterior forefoot, it likewise creates a rearfoot dorsiflexion moment and a forefoot plantarflexion moment. Therefore, the Low-Dye strapping will reduce the tensile force on the plantar fascia since the Low-Dye strapping, basically, performs the same mechanical function as the plantar fascia.

This is the beauty of understanding the joints of the foot and lower extremity by using the concept of moments and rotational equilibriium: many therapeutic modalities may be explained mechanically much more precisely than would be possibe without their use.

[Atlas]

Low-Dye strapping causes a anteriorly directed force on the plantar calcaneus and a posteriorly directed force on the anterior forefoot. These two forces will cause a rearfoot dorsiflexion moment and a forefoot plantarflexion moment, especially when the strapping is exerting a large tensile force on the skin of the foot (such as when the foot is in the late midstance phase of gait).

Since the plantar fascia, like the Low-Dye strapping, also causes an anteriorly directed force on the plantar calcaneus and a posteriorly directed force on the anterior forefoot, it likewise creates a rearfoot dorsiflexion moment and a forefoot plantarflexion moment. Therefore, the Low-Dye strapping will reduce the tensile force on the plantar fascia since the Low-Dye strapping, basically, performs the same mechanical function as the plantar fascia.


The forefoot plantarflexion moment made sense to me, but you have opened my eyes to the rearfoot dorsiflexion moment provided by taping.


My original rearfoot mindset regarding the efficacy of low-dye taping of plantar fasciitis conditions centred around reducing the excursion of the medial tubercle. The plane of excursion would of course depend on the horizontal/vertical position of the STJ axis. My original rearfoot mindset was low-dye taping reduced the total excursion of the origin, hence the therapeutic influence on the rearfoot.

But I have ignored and/or not come across the rearfoot dorsiflexion effect of L.D.taping; perhaps at my peril.


I had almost come up with a 'rule' that suggested if L.D.taping is therapeutic, perhaps a root +/- modified device would suffice.

Now that you have got me on a rearfoot dorsi-flexion wavelength, I might have to dilute the rule as other devices and modifications dorsi-flex the rearfoot more potently.

[Kevin Kirby]

The forefoot plantarflexion moment made sense to me, but you have opened my eyes to the rearfoot dorsiflexion moment provided by taping.

My original rearfoot mindset regarding the efficacy of low-dye taping of plantar fasciitis conditions centred around reducing the excursion of the medial tubercle. The plane of excursion would of course depend on the horizontal/vertical position of the STJ axis. My original rearfoot mindset was low-dye taping reduced the total excursion of the origin, hence the therapeutic influence on the rearfoot.

But I have ignored and/or not come across the rearfoot dorsiflexion effect of L.D.taping; perhaps at my peril.

I had almost come up with a 'rule' that suggested if L.D.taping is therapeutic, perhaps a root +/- modified device would suffice.

Now that you have got me on a rearfoot dorsi-flexion wavelength, I might have to dilute the rule as other devices and modifications dorsi-flex the rearfoot more potently.

Low-Dye strapping will also cause a mechanical effect on the subtalar joint (STJ), however this effect is weaker than its effect on the midtarsal joint (MTJ). If the strapping can prevent flattening of the medial longitudinal arch (MLA), then the increased ground reaction force that occurs plantar to the medial metatarsal rays will cause increased STJ supination moment (or decreased STJ pronation moment).

Certainly the rearfoot dorsiflexion moment produced by Low-Dye strapping is very important along with its ability to produce a forefoot plantarflexion moment. The magnitude of rearfoot dorsiflexion moment and forefoot plantarflexion moment produced by the strapping (and the plantar fascia, for that matter) will be dependent on the height of the longitudinal arch of the foot. The higher the arch, the greater the moments. In a very flat arched foot, virtually no rearfoot dorsiflexion moment or forefoot plantarflexion moment will be produced by the strapping (and again, the same goes for the plantar fascia).

I think many clinicians make the mistake to assume that if Low-Dye strapping works, then foot orthoses should work just as well. Foot orthoses work by modifying the ground reaction forces on the plantar foot (all compression forces) whereas Low-Dye strapping works by adding tensile forces to the skin of the foot to cause its mechanical effect. It is for this reason that Low-Dye strapping generally is sometimes more effective for symptoms caused by excessive arch flattening moments, such as plantar fasciitis, than foot orthoses are.

[Paul Harradine]

Sorry, bit late on this!

Harradine PD, Herrington L, Wright R. The effect of low dye taping upon rearfoot motion before and after exercise. The Foot. 11(2):2001. p57-61

We found during the initial 60% of stance phase rearfoot motion (pronation angle, max pronation and velocity of pronation) was not significantly altered by Low dye taping. Intial RCSP was more inverted, but this was lost after a brief duration of treadmill walking.

I've been using the F-Scan in-shoe for a while now and find low-dye taping increases 1st MPJ loading and makes force time curves much more 'm' shape in the symptomatic cases I see. Interesting how the windlass can appear to work more effectively without apparently changing rearfoot position or motion.

Paul Harradine MSc BSc(Hons) CertEd
Podiatrist / Director
The Podiatry and Chiropody Centre
Cosham, Portsmouth, UK

[Kevin Kirby]

Sorry, bit late on this!

Harradine PD, Herrington L, Wright R. The effect of low dye taping upon rearfoot motion before and after exercise. The Foot. 11(2):2001. p57-61

We found during the initial 60% of stance phase rearfoot motion (pronation angle, max pronation and velocity of pronation) was not significantly altered by Low dye taping. Intial RCSP was more inverted, but this was lost after a brief duration of treadmill walking.

I've been using the F-Scan in-shoe for a while now and find low-dye taping increases 1st MPJ loading and makes force time curves much more 'm' shape in the symptomatic cases I see. Interesting how the windlass can appear to work more effectively without apparently changing rearfoot position or motion.

Paul Harradine MSc BSc(Hons) CertEd
Podiatrist / Director
The Podiatry and Chiropody Centre
Cosham, Portsmouth, UK

Paul:

If the primary effect of the low-Dye taping is to cause a forefoot plantarflexion moment (with probably more effect on the medial column than lateral column) then your F-scan results make sense. The low-Dye taping crosses the midtarsal joint (MTJ), and does not cross the subtalar joint (STJ). Because of this, it will have much more mechanical impact on the MTJ than on the STJ. That is not to say that it will not have an effect on the STJ, but it will likely be much less visible.

A good example of how the windlass can be changed without an apparent change in rearfoot position or motion is to take a foot that is maximally pronated at the STJ in relaxed bipedal stance, and then add some extra STJ pronation moment to it by having, for example, the foot stand on a 10 degree valgus wedge.

Has the rearfoot position changed? No.

Has the rearfoot moved? No.

However, now try a Hubscher maneuver on both feet and which foot condition do you think will require more force to dorsiflex the hallux? The one with the valgus wedge. The supination resistance test will also likely require more force (Kirby KA, Green DR: Evaluation and Nonoperative Management of Pes Valgus, pp. 295-327, in DeValentine, S.(ed), Foot and Ankle Disorders in Children. Churchill-Livingstone, New York, 1992).

It is the kinetics of the foot that will alter the kinematics. However, the kinetics can change without an alteration of the kinematics. Thinking in terms of rotational equilibrium and kinetics greatly helps in understanding these findings.

[Paul Harradine]

Hi Kevin

I completely agree with your reply. Infact, we demonstrated your valgus posting example to some extent in:

Harradine PD & Bevan LJ : The effect of rearfoot eversion upon maximum hallux dorsiflexion. Journal of the American Podiatric Medicine Association 9(90);2000

When fitting orthoses though, do you still like to see an 'improvement' in rearfoot position and motion? Or do you look for static test improvements such as Hubscher standing on the appliances etc?

Regards

Paul Harradine

[Craig Payne]

do you still like to see an 'improvement' in rearfoot position and motion? Thats what started this thread....we have found NO correlation to dynamic changes in rearfoot position/motion and clinical outcomes (ie symptom improvement)

[Paul Harradine]

Hi Craig, thanks for the reminder on how the thread started.

It isn't however the question I asked Kevin. I was interested if a podiatrist with the wealth of clinical experience such a Kevin still 'likes to see an 'improvement' in rearfoot position and motion'. I then asked about static tests on orthoses (unshod!) such as the Hubscher.

Sorry for any confusion

Paul

[Craig Payne]

I then asked about static tests on orthoses (unshod!) such as the Hubscher.A reduction in the force to do that test when standing on orthoses (static test) appears to be more predictive of clincial outcomes than changes in the pattern of rearfoot motion (a dynamic test) ---- we starting the RCT to further test and refine this next week.

(Sorry about short sharp answers ---- too many deadlines, too many confernece abstracts due, too many grants to write .... and the students due back Monday :eek:

HINT TO STUDENTS IF YOU WANT TO PASS = don't ask me how the holiday went
:cool:

[Lawrence Bevan]

I would have to agree that in walking most orthotics dont influence rearfoot position hugely or consistently so. Changes one may see are often related to the MTJ not STJ, if one can draw an artificial anatomical line between them.

Less bulging of the midfoot medially under the malleolus, less abductory twist, less knee rotation, longer stride etc are the things you do see and are related to MTJ position. Through altering MTJ position can one alter moments in the STJ? Yes. Does altering the MTJ postion change the ability of the 1st MTP to dorsiflex? Yes. I find although orthotics may not change heel eversion one iota it is unsual to have a successful one that does not alter MTJ pronation and this then facilitates the 1st MTP.
Using the f-Scan when trying to deal with FnHL or windlassy problems very rarely does just using say a 3mm pad under the 2-5 MTPs make any difference but use somthing moulded to the foot that supported the arch and suddenly its all TONS easier. Hang on a minute am I saying ..."lock the MTJ".... ????!!!! Hmmm whats that a stump? you look familiar, I feel the urge to go around you.....

Running however I find "clinically" or empirically that heel eversion is tied to symptoms and is useful to use as a marker for orthotic effect. My theory is that the MTJ pathology is still occuring but because of running limb varus and increased lateral to medial and posterior to anterior directed force the heel everts much more significantly with it.


Ramble, ramble, ramble, burble, burble.

Lawrence Bevan
Staff Podiatrist
Gracelands, Memphis Tennessee
and Area 51

[Paul Harradine]

Craig - It would be great if there were static markers/tests that could determine (to some extent) the success or otherwise of foot orthoses. I've been using the Hubscher for a while now, and then F-scanning, and find that a substantial improvement in Hubscher does correlate with improved in-shoe gait parameters. I await your results!

I'm in the process number crunching some research on the reliability of the Hubscher, Max pronation and supination resistance tests. Good sample size, inter and intra groups. Just getting my head around the stats, but initial results show poor to moderate on most tests, max pronation being the least reliable.

Lawrence - great points, but reduce the coffee intake maybe? 'locking' the MTJ, whatever next? I've lost the key to that one.

I think our main issue is the fact that I certainly was taught 'Rootian' theory, very much joint position and motion and supplying orthotics to change rearfoot motion / position. However, when qualified I prescribed these orthotics and people got better. The same year we read the 'normal foot' does not 'work in neutral' and now orthotics may not even change rearfoot motion / position. However (and this is where the thread came from...i know craig!) rootian orthotics can work for many people, but were they putting the foot in STJN (probably not then)?, reducing moments across the STJ reducing symptom related moments?, or reducing tension in the medial band of the plantar fascia and reducing 1st ray dorsiflexory moments allowing windlass etc?. I think I'll go for all three, cover my bases and join Lawrence in podiatry area 51.

regards to all.

Paul

[Lawrence Bevan]

I'll get u a new key cut

[Paul Harradine]

I think it's available at the 'axes obliquity' store. I have looked there myself a while ago but could not find it

[Kevin Kirby]

Hi Craig, thanks for the reminder on how the thread started.

It isn't however the question I asked Kevin. I was interested if a podiatrist with the wealth of clinical experience such a Kevin still 'likes to see an 'improvement' in rearfoot position and motion'. I then asked about static tests on orthoses (unshod!) such as the Hubscher.

Sorry for any confusion

Paul

Paul and Craig:

I am not that interested in changes in changes in rearfoot position in relaxed bipedal stance, since they don't often change. However, I am very interested in changes in gait function and symptom improvement. Very often the changes with foot orthoses are seen to occur at the midtarsal joint level, which rearfoot measurements won't necessarily show. However, foot orthoses often do change rearfoot motion in gait.

The treatment goal for my patients receiving foot orthoses are as follows:

1. Reduce pathological loading forces on injured structural components.

2. Optimize gait function.

3. Not cause other pathologies or symptoms in accomplishing goals #1 and #2.

Nice discussion, Paul.

[Paul Harradine]

Thanks Kevin

Paul and Craig:

Very often the changes with foot orthoses are seen to occur at the midtarsal joint level, which rearfoot measurements won't necessarily show. However, foot orthoses often do change rearfoot motion in gait.

I'm glad you said that. I often see alterations in rearfoot motion with foot orthoses. Worried it was just me and Lawrence seeing this! Of course it may be the caseloads we are seeing. With your three step treatment goals , would you expect to see a change in rearfoot motion more in a running orthoses prescrition (for example, designed for the type of runner who is maximally pronating but still maintaining an arch, with post tibial tendonitis?).

Have a good weekend

Paul

[Craig Payne]

We do see rearfoot motion changes in some patients, we don't see them in others ---- what I am saying is that we have shown that there is no prospective correlation with changes in rearfoot motion and symptom changes.

[Atlas]

I don't read much research, I just skim the take-home-message...if I am lucky.


If we are to believe that rearfoot changes don't always occur despite aggressive rearfoot 'correcting' devices, is this measured by getting the subject to stand on the orthotic? Without the heel counter of a shoe holding the heel on the orthotic? Or is the orthotic strapped to the foot?

Has some research been done with subjects in plastic tranparent shoes?

[Craig Payne]

If we are to believe that rearfoot changes don't always occur despite aggressive rearfoot 'correcting' devices, is this measured by getting the subject to stand on the orthotic?
We did it by measuring frontal plane translation of malleoli relative to a reference point on shoe with and without othoses (within subject design - used digital video frames at several ponts in the stance phase) - ie if the horizontal distance between the reference point and lateral malleolus increases and the horizontal distance between the reference point and medial malleolus decreases --> more inverted rearfoot (and vice versa)

Irene McClay's group that showed some people pronate more in inverted orthoses, used a cluster marker design attached to the calc via small hole in heel counter (she did tell me how much it weakened te heel counter, but can't recall - it was not much)

Our current work is using running sandals, so we can attach a comprehensive marker set to the bony landmarks -- but that suffers as there is no heel counter... its all about trade offs in this business.

[Kevin Kirby]

Thanks Kevin



I'm glad you said that. I often see alterations in rearfoot motion with foot orthoses. Worried it was just me and Lawrence seeing this! Of course it may be the caseloads we are seeing. With your three step treatment goals , would you expect to see a change in rearfoot motion more in a running orthoses prescrition (for example, designed for the type of runner who is maximally pronating but still maintaining an arch, with post tibial tendonitis?).

Have a good weekend

Paul

Paul, I like your questions. Keep them coming.

Rearfoot motion is often difficult to observe clinically since the changes that occur are hidden by the heel counter of the shoe. However, orthoses commonly affect transverse plane knee position, stride length, relative percentage of stance phase that is propulsion, and midtarsal joint motion.

The more inverted the orthosis, with the more medial heel skive, then the more likely rearfoot changes will occur. I use this type of orthosis prescription for runners with pathology cause by excessive subtalar joint (STJ) pronation moments (e.g. medial tibial stress syndrome) or walkers with pathology caused by excessive STJ pronation moments (e.g. posterior tibial dyfunction). These orthoses very definitely alter the kinematics of the rearfoot and lower extremity during both walking and running.

However, the orthoses that I make for patients with a condition that may be caused by excessive rearfoot plantarflexion and forefoot dorsiflexion moments (e.g. plantar fasciitis) will often show little change in rearfoot kinematics since I don't necessarily invert or add a medial heel skive to these orthoses.

[Kevin Kirby]

Using the f-Scan when trying to deal with FnHL or windlassy problems very rarely does just using say a 3mm pad under the 2-5 MTPs make any difference but use somthing moulded to the foot that supported the arch and suddenly its all TONS easier.

Lawrence Bevan
Staff Podiatrist
Gracelands, Memphis Tennessee
and Area 51

Lawrence:

Excellent observations. Addition of a 3 mm pad under the 2nd-5th metatarsal heads adds a subtalar joint (STJ) pronation moment which will tend to cause the foot to often have more late midstance pronation. However, if you use the same forefoot pad with a medial heel varus wedge and a medial longitudinal arch pad, the foot shows dramatic increases in stride length, gait stability and foot comfort. But why??

The medial heel varus wedge and medial longitudinal arch pad add a STJ supination moment in early stance phase to help decelerate STJ pronation which then, during the latter half of stance phase, works with the 2-5 pad ( that causes a STJ pronation moment) to stabilize the rearfoot. Counteropposing moments on the STJ is one of the keys of this type of "padding" therapy which I have been using in my lecture demonstrations for the past 20 years.

This idea of counteropposing moments has been used by structural engineers for years in stabilizing tall antennaes by placing cables under tension on opposite ends of the antenne, attached to the ground, to create counteropposing moments to create structural stability of the antenna. A rearfoot varus wedge and forefoot valgus wedge accomplish this same mechanical effect on many feet by applying counteropposing moments across the STJ axis.

[Paul Harradine]

Hi Kevin, thanks again for the reply

This is the problem I have with the idea that first ray dysfunction / windlass dysfunction is resonsible for all foot related ills ( i know criag may not have been saying this, but sometimes it seemed that way!). I understand that a FnHL can theoretically 'cause pronation'. And sometimes maybe it does....but in cases when there is a 10 degree tibial varum? Would the large degrees (and velocity) of STJ pronation seen in these patients at contact phase be due to a FnHL? In these cases would we expect, and prescribe, to 'improve' rearfoot kinematics? If this patient was a runner, and had MTSS, would we only expect good results if we did improve this rearfoot motion? Although this tibial varum may result in increased tension in the medial band of the plantar fascia etc, could it possible be the initial pronation velocity / tibial loading responsible for symptoms?

Cheers again

Paul

[Craig Payne]

The way I explain it to students is like this:

Imagine a foot that has pronated to end range of motion at the STJ with a huge amount of force. There will be bone on bone contact, that will hurt due to the compressive forces. The post tib will have to work hard (--> maybe MTSS, post tib dysfunction).

You then put an orthotic under the foot and watch them walk --- imagine there is no difference in the way they walk (ie the kinematics have not changed) - they come back 2 weeks later and the symptoms are gone.

The question then, is why did they get better even when there is no improvement in the pattern of rearfoot motion (ie kinematics) (which is what our research showed)

What has happened is this - the STJ has still gone to end range of motion and there is bone on bone contact, but the joint surfaces are only just touching each other and there are not the huge compressive forces that were previously hurting ... ie the foot orthoses have altered the kinetics (ie forces). The post tib will not have to work as hard (symptoms their reduce), as the kinetics have changed.

To get symptom relief, the kinetics (forces, work) have to be altered --- it does not seem to matter if the kinematics (motion, position) are altered or not.

Motion and position do not damage tissues (..yet the profession is very hung up on this). Forces damage tissues.

The force to establish the windlass being lowered with foot orthoses is just one measure of what is happening to the forces. Our research has shown that this lowering of that force is probably related to outcomes.

[Kevin Kirby]

Hi Kevin, thanks again for the reply

This is the problem I have with the idea that first ray dysfunction / windlass dysfunction is resonsible for all foot related ills ( i know criag may not have been saying this, but sometimes it seemed that way!). I understand that a FnHL can theoretically 'cause pronation'. And sometimes maybe it does....but in cases when there is a 10 degree tibial varum? Would the large degrees (and velocity) of STJ pronation seen in these patients at contact phase be due to a FnHL? In these cases would we expect, and prescribe, to 'improve' rearfoot kinematics? If this patient was a runner, and had MTSS, would we only expect good results if we did improve this rearfoot motion? Although this tibial varum may result in increased tension in the medial band of the plantar fascia etc, could it possible be the initial pronation velocity / tibial loading responsible for symptoms?

Cheers again

Paul

Paul:

I really don't believe that functional hallux limitus (FnHL) is a cause of pronation, but is a result of a multitude of factors, with excessive subtalar joint (STJ) pronation moments being one of them. Other causes of FnHL can include a long first metatarsal, decreased medial longitudinal arch (MLA) height, a short hallux proximal phalanx and a larger radius of curvature of the first metatarsal head in the sagittal plane. By using a wooden model in a couple of demonstrations I performed at the PFOLA meeting in Boston a few months ago, I was able to show just how changes in MLA height can cause FnHL. Pronation and MLA collapse comes first, FnHL comes second, in my opinion.

Eric Fuller made a good case for the plantar fascia being one of the structures that can resist STJ pronation moments which, in turn, can be used to suggest how STJ pronation moments affect FnHL (Fuller, Eric A: Center of pressure and its theoretical relationship to foot pathology. JAPMA, 89 (6):278-291, 1999; Fuller, Eric A: The windlass mechanism of the foot: A mechanical model to explain pathology. JAPMA, 90:35-46, 2000).

In Craig Payne's excellent reply, he discusses how he teaches the concept of interosseous compression forces within the sinus tarsi as a method to help in understanding how the posterior tibial may be affected by STJ pronation moments. I very much like Craig's approach. I introduced this concept of interosseous compression forces within the sinus tarsi and how it may affect posterior tibial contractile activity to cause STJ supination in my first paper on STJ rotational equilbrium (Kirby, KA.: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989).

Tibial varum does not cause a particularly strong STJ pronation moment since large degrees of tibial varum may cause a STJ supination moment. I can think of many other types of structural deformities that will cause more STJ pronation moment than increased tibial varum.

[Craig Payne]

Tibial varum does not cause a particularly strong STJ pronation moment since large degrees of tibial varum may cause a STJ supination moment. I think a lot of people miss that last point. Also a tibial valgum and/or genu valgum provide a supinatory moment to the STJ. How often do you read in the podiatric literature about them pronating the foot.tibial varum If someone has a tibial varum, yes the foot has to pronate to get flat on the ground, but since when has the "motion" of pronation or the "position" of pronated been pathologic - it never has (hence my comment above about the profession being hung up on motion and position. If a foot pronates excessively, it is still winthin the "range of motion" of the posterior tibial tendon - so how does pronation damage the posterior tibial tendon? It will only damage the post tib of the FORCES are high, so the muscle has to work harder. If the forces pronating in a foot in those with tibial varum are low, whats the problem?

I gotta go - off now to give the 2nd years their first biomech lecture for the semester - its the "half of what we teach you this semseter is wrong, but we don't know which half it is" lecture...

[Kevin Kirby]

I think a lot of people miss that last point. Also a tibial valgum and/or genu valgum provide a supinatory moment to the STJ. How often do you read in the podiatric literature about them pronating the foot.

In a paper soon to be published in JAPMA, Bart Van Gheluwe, Friso Hagman and I studied the effects of simulated genu valgum and genu varum on a group of normal subjects walking over a force plate and pressure mat with some very interesting results. We calculated that genu valgum does indeed cause a STJ supination moment in late midstance.

If someone has a tibial varum, yes the foot has to pronate to get flat on the ground, but since when has the "motion" of pronation or the "position" of pronated been pathologic - it never has (hence my comment above about the profession being hung up on motion and position.

Until podiatry students and podiatrists fully understand the concepts of moments, rotational equilibrium and external and internal forces acting on the foot and lower extremity, motion and position will still be regarded as being the cause of injuries by the podiatry profession. It has been and it will be a long, hard intellectual battle, but we have made significant progress in this regard within the past 15 years. These efforts to keep us more in line with the thought processes and work from the international biomechanics community will allow podiatric biomechanics stay at the forefront of mechanical and surgical treatment of foot and lower extremity mechanically-based pathologies.

Personally, I'm very optimistic and glad that we aren't still languishing under the influence of vertically balanced foot orthoses, compensations for forefoot deformities, subtalar joint neutral theory and the two-axis model of the midtarsal joint, even though I am sure that many "podiatric biomechanics experts" still teach these concepts. Thanks, Craig, for your research efforts in this regard.

[Paul Harradine]

Hi Craig and Kevin

I've lost the thread here I think, I've just read back over previous messages. I don't think we are disagreeing. I was saying that in certain cases i like to see an improvement in rearfoot motion. In cases of a maximally pronated runner, maintaining and arch, with post-tib tendonits, these patients only significantly seem to get better if I see such an improvement. This obviously links in to forces.

I've quoted it in some of my papers: 'its not pronation that hurts, but the structures stopping the pronation'.....

Regards

Paul


To put my point more concisely, STJ pronation (motion) lowers the arch and increases tension in the medial band of the plantar fascia (force?). This, is itself, can cause problems related to an FnHL. Due to the nature of tissue loading etc, I often see cases where I would expect to see

[Paul Harradine]

sorry about the junk after my name on the last bit. Meant to be to another thread!

[Craig Payne]

'its not pronation that hurts, but the structures stopping the pronation'Jumping from a tall building (motion) does not kill you. Hitting the ground (forces) does.

[Kevin Kirby]

Jumping from a tall building (motion) does not kill you. Hitting the ground (forces) does.

Or put another way, it's not the acceleration that causes injury, it's the deceleration.

[Atlas]

Another analogy I would throw in, is that motion is the tired old saggy housewife, and force is the new sleek gravity-defying mistress. But lets not forget who would be more reliable at cooking the roast and picking up the kids.


I have two problems with its 100% force and 0% motion.
1. How can these 2 phenomena be independent of each-other?
2. Awareness of pathological motion and the ability to alter it is a powerful clinical tool.


1. How can these 2 phenomena be independent of each-other? How can the fellow who splatters himself on concrete do so without plummeting from a height. What else can provide such a FORCE?

What about the analogy of a baseball catcher or cricket wicket-keeper. When catching a ball at speed, the keeper wisely accepts the ball out in front of his body, but finishes the 'catch' behind him. The motion of his hands in the same direction as the ball gradualises the deceleration. How can motion be completely irrelevant here? No motion equals bruised hands.


2. Awareness of pathological motion and the ability to alter it is a powerful clinical tool.

Lets take a posterior impingement of the ankle for instance; for example a clinical os trigonum. End-range plantar-flexion is pathological and symptomatic. Restrict that range to short-of-its-limitation, and the patient is happy. (Restrict it for days and perhaps one has an impact on adjacent secondary soft-tissue inflammation if it existed concurrently). Yes a plantar-flexion moment around the ankle could be aggravating, but only at the end of (PF) range. Limit end-range plantar-flexion with an strapping technique, and the plantar-flexion moment provided by kicking a football or kneeling on your heels becomes tolerable.
Critics may suggest that the strapping is providing a neutralising dorsi-flexion moment, but how then can one extrapolate and suggest that motion is entirely irrelevant?

What about an unstable ankle? An ankle with a sloppy mobile anterior-drawer? An ankle that is multi-directionally hypermobile is an inevitable accident that will progressively happen. Osteoarthritis in the talo-crural joint is inevitable. Surrounding musculo-tendinous structures are then 'called up' to function in a manner that they were not intended; to remain hyper-tonically overactive to provide some motion check and joint stability. Stop the extraneous motion (albeit with stabilising FORCES), and reduce signs and symptoms.

Turning your head to do a head check in a car involves everyday movement and presumably everyday forces. But what happens if we sustain the position? Why the signs and symptoms. The forces haven't suddenly become pathological. They haven't increased. The forces have been sustained/prolonged. In terms of motion, this suddenly hasn't become pathological, nor increased; but the limit of motion has been sustained. In this limit of motion, agonists have shortened, antagonists lengthened, some passive tissues have stretched (tensile forces), while others are impinging (compressive forces).


If I was a post-tib musculotendinous structure, I would not want to be 'connected to' a foot that's motion permits my insertion to drift/drop further and further away. If you want me to jump from a building, give me the 1st floor, not the 6th. In the early part of stance, the navicular drop/drift is lengthening the unit. At the same time it is contracting eccentrically to control/decelerate/oppose this. IMO, low-dye taping has a significant impact (short-term at least) on tib-post dysfunction. The force crowd will suggest that the low-dye taping provides a sufficient force to counter-act this pathology. The motion person may suggest that it keeps the origin and insertion of tib-post closer together. Limit motion = limit length = reducing tensile stress.

Take motion out of the equation, and you don't get impingement and sprains etc. I could take one of Ali's punches if he was only allowed 20 degrees elbow extension. His force capacity (musculature) would be the same; but motion augments momentum and hence the force to floor me.



All the force talk makes sense and can be justified. But I have a problem with 100% force and 0% motion as contributing factors to injury. Despite what the latest research suggests, we need health clinicians (especially students) thinking about forces and motion…not just the former.




Ron.

[Kevin Kirby]

I have two problems with its 100% force and 0% motion.
1. How can these 2 phenomena be independent of each-other?
2. Awareness of pathological motion and the ability to alter it is a powerful clinical tool.

Newton's Second Law of Motion states that the acceleration of an object is directly proportional to the net force acting on the object and inversely proportoinal to the mass of the object. F = ma.

Because of this interrelationship of motion and force, then you are correct, Ron, that one can not say that injury is caused only by force and not by motion. Acceleration is the change of velocity over time or for those that have had calculus, acceleration is the first derivative of velocity. Velocity is the change of displacement of an object over time. Therefore, accleleration is the second derivative of displacement. Therefore, force and motion are directly interrelated by using Newton's Second Law of Motion.


1. How can these 2 phenomena be independent of each-other? How can the fellow who splatters himself on concrete do so without plummeting from a height. What else can provide such a FORCE?

What about the analogy of a baseball catcher or cricket wicket-keeper. When catching a ball at speed, the keeper wisely accepts the ball out in front of his body, but finishes the 'catch' behind him. The motion of his hands in the same direction as the ball gradualises the deceleration. How can motion be completely irrelevant here? No motion equals bruised hands.

Helpful here is the Principle of Conservation of Linear Momentum. Here we should use the concept of the impulse-momentum theorem where:
impulse = change in momentum. Impulse of a force is a product of the average force and the time interval during which the force acts: Impulse = F x t.

Momentum of an object is the product of the object's masss and velocity: Momentum = m x v.

Using the Principle of Conservation of Linear Momentum, it can be said that the total linear momentum of an isolated system remains constant (i.e. is conserved). Therefore, for the baseball catcher, the average velocity of the decelerating baseball times its mass will equal the average velocity of the catcher's hand and mitt times its mass. The faster the ball is thrown and the greater the mass of the ball, then the more momentum, so that the catcher will need to absorb more momentum during catching the ball due to conservation of momentum.

All the force talk makes sense and can be justified. But I have a problem with 100% force and 0% motion as contributing factors to injury. Despite what the latest research suggests, we need health clinicians (especially students) thinking about forces and motion…not just the former.

I would agree that we should not say that it is 100% force and 0% motion, since force and motion are tightly interrelated. But I would say that clinicians and students need to know about forces, motion, mass, moment of inertia, moments, moment arms, linear and rotational equilibrium, stress, strain, elastic modulus, and all the other basic mechanical concepts that affect the structural components of the human body. However, it is unlikely that all podiatrists or podiatry students will have a firm grasp on these concepts during my lifetime. Because of this, for many years to come, these important topics of biomechanics will be thought of as "advanced concepts" for podiatrists and will not be considered as basic concepts as first year engineering students consider them.

[Kerry_Rambarran]

Fallacies:

Applying a linear equation to a number of joints that move in three axes of motion, thereby oversimplifying the issue so it does not consider angular impulse

Oversimplifying forces that act on the stance foot as an average force that is then applied to the linear equation; ignoring the fact that the swinging limb contributes momentum (constantly changing in a fashion that is unrepresentative by being averaged) to the stance limb.

Attempting to apply these Newtonian “concepts” to a system that is clearly neither closed nor isolated.

Current and past methods in empirical Biomechanics (with and without podiatric input) cannot discern statistically significant differences with and without CFO intervention. However, therein lies numerous clinical significances, which makes these practices successful.

Perhaps in future, as methodologies and apparatus evolve, such clinical success, "may" be empirically explained.

I for one look forward to such prospects.

-Kerry

[davidh]

Attempting to apply these Newtonian “concepts” to a system that is clearly neither closed nor isolated.



Hi Kerry,
You missed out diurnal variation as it applies to the human lower limb.

I have to point out that applying Newtonian concepts to a system that is clearly neither closed nor isolated is not an activity exclusive to podiatriy.

Newtonian concepts are widely used in bioengineering - when designing replacement joints for example, and by orthopaedic surgeons, when replacing worn joints.
Regards,
David :cool:
David Holland BSc(Hons) Pod Med, MSc(Bioeng).

[Kerry_Rambarran]

It is true that other professions use this approach during Finite Element Analysis. Currently initial research and testing by companies such as Smith and Nephew use simulators for data pertaining to joint kinematics and durability. Based on trial data presented at academic conferences this is an apparently rigorous process.

Eventually, as dialogue between patients and practitioners makes its way back to the drawing board (bioengineers), refining the model indirectly makes the model less finite and more real. Which (relating back to the original topic of discussion posted by Dr. Payne) may account for more clinical versus statistical significance. Again this is a product of research methodologies.

I have noticed less gait "noise" in those with only a knee arthoplasty rather than the hip. Perhaps this may be due to the fact that during stance the knee mainly flexes and extends through the sagittal plane (medio-lateral axis), i.e. mainly one degree of freedom rather than three of the hip.

While this curent approach with the hip may never return patients back to their previous state (of 100%), postoperatively their quality of life is mostly better….a great thing!

Data from my last research what suggested (within subject) significant differences between CFO conditions. However statistical differences were not noted after ensemble averaging of data (a common practice in empirical research).

[Craig Payne]

Kerry - thanks for the input...Eventually, as dialogue between patients and practitioners makes its way back to the drawing board (bioengineers), refining the model indirectly makes the model less finite and more real. Which (relating back to the original topic of discussion posted by <Craig>) may account for more clinical versus statistical significance. The approach we are trying to take is to measure using different "models" what actually happens to the patient mechanically and correlate that to outcomes --- not outcomes as a change in the biomechanical parameters, but outcomes in terms of symptom reduction (using validated measures, such as the FHSQ (http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=235)) .... the ultimate aim to to find predictors of outcomes. from the study I mentioned in the first post, changes in the pattern of rearfoot motion was not related to clinical outcomes ---- some things are getting clearer. We have just started recruiting for a couple of RCT's to test what we found.

Kerry - thanks for those abstracts of a few weeks ago. Also, I will be in Ottawa in November.

[Kevin Kirby]

Fallacies:

Applying a linear equation to a number of joints that move in three axes of motion, thereby oversimplifying the issue so it does not consider angular impulse

Kerry, I have found that in my 20 years of teaching podiatrists and podiatry students biomechanical concepts there must be some simplification of concepts so that they can grasp the basics. As they become more knowledgeable, they can more easily understand more complex concepts. In biomechanical modelling, using uniplanar, simplified models are acceptable as long as you understand their inherent limitations.

Oversimplifying forces that act on the stance foot as an average force that is then applied to the linear equation; ignoring the fact that the swinging limb contributes momentum (constantly changing in a fashion that is unrepresentative by being averaged) to the stance limb.

Both internal and external forces acting on the stance phase foot need to be considered when determining the forces acting internally within the foot. Of course the swing limb needs to be included if one is interested in the energetics of locomotion. However, if one is interested in something such as the direction and magnitude of moments acting across the subtalar joint axis at any instant in time, the mechanical contributions of the swing phase limb may be ignored as long as the spatial location of the subtalar joint axis is known, the center or pressure is known and the direction, magitude and line of action of the ground reaction force vector is also known.

Attempting to apply these Newtonian “concepts” to a system that is clearly neither closed nor isolated.

Newtonian concepts are still used in physics, engineering and biomechanics, to this day. I agree with David Holland that they are widely used in many fields. I don't understand which of Sir Isaac Newton's concepts you don't like??

Current and past methods in empirical Biomechanics (with and without podiatric input) cannot discern statistically significant differences with and without CFO intervention. However, therein lies numerous clinical significances, which makes these practices successful.

Have you read the papers by Mundermann et al and Williams et al?(1. Mündermann, A, Nigg BM, Humble, RN, Stefanyshyn, DJ: Foot orthotics affect lower extremity kinematics and kinetics during running. Clin Biomechanics, 18(3):254-262, 2003. 2. Williams, D.S., McClay-Davis, I., Baitch, S.P.: Effect of inverted orthoses on lower extremity mechanics in runners. Med. Sci. Sports Exerc. 35:2060-2068, 2003.) These researchers were able to discern statistically significant biomechanical differences with and without custom foot orthoses. As I have been lecturing for years, orthoses affect moments more than motion.
[/QUOTE]

I enjoy your input and criticisms, Kerry. You are obviously very knowledgable in biomechanics. I am interested in your research at Ottawa Hospital if you could let us know more about it, it would be greatly appreciated. We are always looking for new lecturers on biomechanics here in the States. Have you published any of your research yet?

[Kerry_Rambarran]

Ahh, good. I think it is important to acknowledge the inherent limitations of applying linear physical equations to the foot.

With respect to the two research articles by Mundermann et al. and Williams et al., both discussed kinematic parameters of the whole foot (i.e. one segment models).

The Kinetic parameters discussed by Mundermann et al. included peak vertical loading rates (whole foot). Significant differences were found up the kinetic chain including the foot.

Conversely, Williams et al. kinematic found no significant differences in ankle eversion / inversion, however, peak rear foot inversion moments and work were significantly reduced during inverted CFO trials. The methodology used by this paper still analyses the foot as a single segment, due to limitations. is this acceptable? Perhaps for now.

This is the paradox:
1.To better understand the foot and ankle, dynamic, rather than static physical measurements are necessary (methodological limitations).
2.To better understand the both internal and external forces (both are important) that act on the foot and ankle we need to move towards a more fluid model that encompasses more than two segments (a team at Penn State is currently working on that).

Looking at the GRF with respect to the STJ is acceptable when looking at instances during stance. What methodologies can we use to the question is how does one take several of these instances and put them together to get a better understanding of foot function (normal or pathological).

If we look at GRF or CoP with respect to the STJ at best we can view the foot a two segment model. Again is this an appropriate approach?

-Kerry

[Atlas]

I will not even dare to enter a debate far beyond my capabilities (advanced kinematics and kinetics).

Students and young graduates (and maybe a few oldies) have enough trouble with the biomechanics in day-to-day musculo-skeletal medicine. And in view of this, and my feeling that simple basic (albeit slightly flawed) concepts adequately describe what may be wrong and what we as clinicians must do to address it, teaching must remain simple. And teachers should be comfortable with this.


Even if and when we discover the complex answers, I can't see how this can be re-formatted in a simple teaching version.

In the ideal world though, yes, lets get the complex correct answers and transfer all of this across to the learners.

[Kevin Kirby]

Ahh, good. I think it is important to acknowledge the inherent limitations of applying linear physical equations to the foot.

With respect to the two research articles by Mundermann et al. and Williams et al., both discussed kinematic parameters of the whole foot (i.e. one segment models).

The Kinetic parameters discussed by Mundermann et al. included peak vertical loading rates (whole foot). Significant differences were found up the kinetic chain including the foot.

Conversely, Williams et al. kinematic found no significant differences in ankle eversion / inversion, however, peak rear foot inversion moments and work were significantly reduced during inverted CFO trials. The methodology used by this paper still analyses the foot as a single segment, due to limitations. is this acceptable? Perhaps for now.

The prevailing research seems to indicate that moments are affected much more than motion by foot orthoses. Benno Nigg has his "preferred movement pathway" theory that states that the individual will tend to move in a certain movement pattern during gait. Therefore, this is why he feels that motion is relatively unaffected by foot orthoses. However, when I lectured with Benno at the University of Calgary a few years back, he said his knee feels better with foot orthoses so he knows that foot orthoses do work, he just couldn't be certain how they work at the time.

I believe that one of the reasons that much of the foot orthosis research to date has not shown much difference in motion of the foot is the foot orthoses used were not corrective enough or were not custom foot orthoses. Clinically, if one wants to see a change in kinematics, the foot orthosis must be quite corrective, often with medial heel skives, inverted balancing positions, rigid plate materials. Without these corrections (i.e. vertically balanced foot orthosis made with a semi-flexible material) the foot orthosis will not resist the motions of the foot enough to show a change in kinematics.

Neil Humble was wise to use such corrective orthoses in the Mundermann et al study and I think that this was one of the main reasons why Mundermann's study showed the changes in kinetics that it did. In addition, in the study by Williams et al, Steve Baitch made Blake inverted orthoses that were used to demonstrate the kinetic changes. The moral of this story is that if you want your research study to show that orthoses change gait kinetics or kinematics, the more corrective the orthosis, the more likely that changes will be seen. In other words, don't use vertically balanced foot orthoses without medial heel skives or without inverted heel cups!

Kinetics of the rearfoot can be changed without a change in kinematics during both walking and running. If the subtalar joint (STJ) is maximally pronated throughout the midstance phase of gait and the patient wears a foot orthosis that relieves their sinus tarsi pain by decreasing the interosseous compression force within the sinus tarsi, but the orthosis is not corrective enough to supinate the STJ out of the maximally pronated position in midstance, then the kinematics of the rearfoot during midstance will not likely change (Kirby, KA.: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989). This is a fact that few biomechanics researchers mention in their papers on the kinetic effects of foot orthoses.


This is the paradox:
1.To better understand the foot and ankle, dynamic, rather than static physical measurements are necessary (methodological limitations).

I agree. However, quasi-static models may be used quite effectively to model the internal forces within the foot and lower extremity. In addition, finite element analysis can be quite effective at determining internal forces. Simon Bartold's research group at Asics currently is using such a model that has defined nearly all the ligaments, muscles and bones of the foot and lower extremity as a way to test mechanical effects on the foot with different sport shoe designs. Dynamics is nice, but statics can tell you a whole lot also.


2.To better understand the both internal and external forces (both are important) that act on the foot and ankle we need to move towards a more fluid model that encompasses more than two segments (a team at Penn State is currently working on that).

I am currently working with Steve Piazza and Greg Lewis from Penn State on STJ axis location in cadavers. They have been trying to determine STJ axis location mathematically by optimization techniques for calcaneal to tibial motion. I recommended some changes in technique that we applied to cadavers last fall when I went to Penn State to help them with their research. Greg is presenting our work on STJ axis location at the GCMAS meeting in Portland, Oregon in a few weeks which I will be attending. In addition, Neil Sharkey is still using his Dynamic Gait Simulator at Penn State to research kinematics and kinetics of gait in cadaver specimens that are "walked" using servomotors attached to the tendons of the foot. Neil and I will be presenting together this June at the WPC at Disneyland Hotel and I hope to collaborate with their group in the future.


Looking at the GRF with respect to the STJ is acceptable when looking at instances during stance. What methodologies can we use to the question is how does one take several of these instances and put them together to get a better understanding of foot function (normal or pathological).

Quasi-static modelling is an acceptable method of taking "snap-shots" of each instance of gait to determine the approximate STJ moments that are occuring at any instant in gait. This can be used to give the clinician a better idea of how STJ moments are affected by pathologies such as PT dysfunction or metatarsus adductus and how treatments such as medial heel skive or Blake inverted orthoses affect STJ moments. That is not to say that gait dynamics is not important, but for the clinician, I have found that the static model is a much better starting point to allow them to progress intellectually toward the greater complexities of gait dynamics.

If we look at GRF or CoP with respect to the STJ at best we can view the foot a two segment model. Again is this an appropriate approach?

The more segments, the greater the complexity. I think a better question is how much complexity do students and clinicians need to optimize their understanding of foot and lower extremity function. I think that this will depend greatly on their previous comfort and knowledge with mathematics and physics.

Chris Nester and Andrew Findlow will be introducing a new model for the midtarsal joint in a new article to be published soon in JAPMA. I have read the article and discussed this model quite a bit with Chris and I really like the direction that Chris and coworkers are headed with the midtarsal joint. I think that having more segments is great for those clinicians who have the capacity to "soak it all in". Unfortunately, in my 20 years of teaching, I have found that most clinicians either don't want to spend the time learning biomechanics or don't have enough basic biomechanics knowledge to understand the complexities of foot and lower extremity biomechanics.

By the way, Kerry, I enjoyed your article and please tell Gordon Robertson that I greatly enjoyed his book "Introduction to Biomechanics for Human Motion Analysis" and have recommended it to many of my students and clinician-students to increase their knowledge of biomechanics.

[NewsBot]

The research that started this thread has been published:

Relationship Between Positive Clinical Outcomes of Foot Orthotic Treatment and Changes in Rearfoot Kinematics
Gerard V. Zammit and Craig B. Payne
J Am Podiatr Med Assoc 97(3): 207–212, 2007 (http://www.japmaonline.org/cgi/content/abstract/97/3/207)
Background: Previous two-dimensional kinematic studies that assessed the effect of foot orthoses on rearfoot motion have yielded mixed results regarding whether control of rearfoot motion is related to symptom relief.

Methods: We sought to determine the effect of foot orthoses on rearfoot motion and to correlate these changes with the degree of symptom improvement in 22 individuals with excessive rearfoot pronation (17 women and 5 men; mean ± SD age, 44.3 ± 16.7 years; mean ± SD weight, 74.9 ± 15.9 kg). Two-dimensional motion-analysis software was used to assess frontal plane rearfoot motion with and without foot orthoses. The mean ± SD Foot Posture Index of the left foot was 8.83 ± 3.54 and of the right foot was 9.22 ± 3.64). The pain and function subscales of the Foot Health Status Questionnaire were then used to determine the degree of symptom relief associated with the orthoses at baseline and 4 weeks later.

Results: Orthoses had a small but statistically significant effect on rearfoot motion, although no significant correlations were found between differences in rearfoot motion with and without foot orthoses and the improvements demonstrated in the Foot Health Status Questionnaire subscales of pain and function.

Conclusions: The effect of orthoses on frontal plane rearfoot motion is considered small and probably insufficient to account for the extent of symptom reduction found in this study. Other parameters of orthotic function, such as kinetic and neuromechanical variables, should be further investigated.