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I have not applied wedges clinically for OA but have thought about the concept for some time. I have a much more simplistic view of how these work- which is purely in the frontal plane. I feel that the lateral wedges tilt the tibia in the frontal plane when the STJ can't accommodate to the wedge. I don't think much internal leg rotation is happening.
In view of all the studies, it seems that lateral wedges have more of an affect on the knee then medial. I assume this is because the STJ has the ability to invert much more than evert, esp in the max pronated patient, which can't evert at all. That being said, most can accommodate better to the varus wedge rather than the valgus at the level of the STJ due more available ROM.
With respects to the max pronated patient (which most knee OA are), they would repond to a lateral wedge much like someone with a triple arthrodesis. Both are standing in heel valgus without the ability to pronate further. As such, the GRF of the lateral wedge must be resolved proximally with little triplanar motion since the STJ has little/no movement. The tibia is thrust medially in the frontal plane and genu valgum is the result.
This is how I see it, I could be wrong....
Nick
From a biomechanical standpoint, it is more accurate to say that the valgus insoles used when treating medial knee OA cause a lateral shift in the center of pressure which will, in turn, cause a decrease in external knee adduction moment. The problem with saying that valgus wedges "tilt the tibia in the frontal plane" is that this does not accurately portray what is happening mechanically. No measureable tibial motion need to occur in order for these valgus wedges to produce the reduction in pressure in the medial compartment of the knee that produces the symptomatic results seen in patients with medial knee OA. One of my previous Thought Experiments explains this mechanical idea more graphically. http://www.podiatry-arena.com/podiat...ght+experiment
In addition, I don't believe that the common idea that feet that are maximally pronated are the only ones that will respond successively to valgus wedging for medial knee OA is mechanically accurate either. I could easily make the argument that since a foot that is not maximally pronated has a greater potential to pronate at the STJ (and, therefore, to abduct more laterally to the longitudinal axis of the tibia), then these patients that are not maximally pronated also have the greatest potential to have a more lateral repositioning of their CoP relative to the longitudinal axis of the tibia due to the valgus wedged insole, and, as a result, have the greatest potential to have decreased external knee adduction moment from these valgus wedges.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
I hear that one of the major running shoe companies has an experimental shoe in development that has a higher density EVA under the lateral side and a softer EVA under the medial side (ie the opposite of the 'motion control' shoe) aimed to mimic the effect of a lateral wedge. If the shoe goes into production, it would be targeted at the medial knee OA group ....
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
I hear that one of the major running shoe companies has an experimental shoe in development that has a higher density EVA under the lateral side and a softer EVA under the medial side (ie the opposite of the 'motion control' shoe) aimed to mimic the effect of a lateral wedge. If the shoe goes into production, it would be targeted at the medial knee OA group ....
A potential problem with creating a shoe of this type is that it may cause injury unless used in the correct patients that have very certain diagnoses. In other words, if a patient that has medial knee pain is told by the shoe store, or other non-medical, personnel that they would benefit from this type of shoe with increased lateral midsole durometer, but that patient also has some other pathology of the medial knee that is caused by increased external knee abduction moments (i.e. valgus moments), such as medial collateral ligament strain or pes anserinus bursitis, then the shoe would likely increase their symptoms, rather than helping them. I wonder if the shoe manufacturer will, therefore, require a prescription for this shoe or if the shoe store personnel will accept medical liability for harming a patient that has been misdiagnosed as to the correct diagnosis for their medial knee pain???? Do you think the shoe manufacturer has thought about this yet?? I guess it depends on which company it is?!
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Some time ago, I completed a study with an orthopaedic colleague looking at the effect of lateral wedging on medial OA. We measured the angle between femur and tibia from erect WB x-rays, and used a Kitaoka pain score to moniter symptomatic changes in a cohort of about 20 subjects who were destined for unicompartmental replacement.
Neither the tibiofemoral angle nor the pain scores showed any significant change, either positive or negative with rearfoot valgus wedging.
regards to all
Simon
Scorpio 22 suggests that a lateral wedge results in genu valgum and this is what would be expected. Athough Simon states that he looked at 20 subjects with medial compartment OA he does not state what size of wedge was used and whether it was used in shoe or simply place under the foot. The degree of varus deformity present would also be useful information and whether or not it was idiopathic oa or as a result of a football injury or as a result of the patient's employment - carpet fitter, electrician etc. Also more importantly he does not indicate what type of foot was wedged. As Scorpio indicates many of the subjects with MCOA have pronated feet but others who perhaps had meniscal surgery may have supinated or normal feet. The difference in foot type could lead to varying results which would then make the results insignificant. As a physiotherapist I look at the foot as part of the body but would consider any treatment which changes the foot to be subject to an initial examination of the foot itself. The use of a lateral wedge may lock the foot into the overpronated position thus keeping the tibia in internal rotation and maintaining a slightly flexed knee - pronation/internal rotation of the tibia/knee flexion being the pattern of movement of the lower leg. This is seen as decreasing the varus deformity which is present in MCOA and lowering the knee adduction moment because the movement in the knee is restricted but the femur is outwardly rotating. Thus to reduce the adduction moment the hip is under increased torsion the the foot is locked into increased pronation neither of which is part of normal gait and both of which may lead to further trauma in a leg which already has a compromised joint. The use of a lateral wedge may be helpful in the short term reduction of pain and in some instances may not have the adverse effects suggested but it would depend on the foot type and subsequent gait pattern.
This is why I find some of the research into lateral wedging worrying - the foot type is not discussed or taken into account - does anyone think that this is important.
I also find the concept very worrying Kathleen, and the reason I wanted to research it further is that at that time, the world of orthopaedics saw long-term lateral wedging of the foot as a viable treatment option for symptomatic medial compartment OA.... but at what cost to the foot? Logically, for any foot type, long term lateral wedging would seem a dangerous thing to do, and even if it did provide symptomatic relief, how long before issues occured at the level of the foot?
In our study, we were most focussed on whether the wedging provided pain relief to a cohort of symptomatic medial OA subjects, with the diagnosis made radiographically. It did not. Wedge angle was 5 degrees valgus. Foot type was not controlled for, because at this time, the orthopods were wedging everyone, regardless of biomechanical profile. We wanted to investigate whether the wedging supported the claim that the medial compartment would be "opened up" by increased (presumed) tibiofemoral valgus. This could not be established radiographically. As a result of this little study, our orthopaedic group stopped prescribing valgus wedging.
On the balance, I am pretty sure this was a good thing.
Regards and happy Christmas to all
Simon Bartold
Lateral wedging for patients with medial OA?!? yes when we see it just theoretical I believe we should relieve the medial side of the knee (Simons study shows no you are wrong maybe because it depends of the cause of OA pain, but good to think "out of the box" again). SO when we treat patients with medial knee pain we need to take the patients into account and then I mean the biomechanical outlining of the feet and body and there gait. In my clinical practice most of the patients with medial OA pain has a torsional problem. So there subtalar joint pronates excessively especially in time while the femur exorotates because of several reasons (muscles, femur position, ...). this means that the tibial endorotates while the femur exorotates and yes, meniscus under stress and so the cartilage too. Also of course the patella tendon and the cartilage under the patella. And because most of the patients have a little tibila varum the medial side of the knee undergoes the most stress wich can cause over time osteo arthritis. SO putting a valgus wedge in our insole by this kind patients, will cause more subtalar pronation and more tibial endorotation and when you don't do anything on the femur exorotation: hmmmm "no good".
The evidence is that an increase in the adductor moment is a major risk factor for medial knee OA.
Lateral wedges have been shown in many lab based studies to reduce the adductor moment at the knee.
Several studies (including Simon's above and one of ours that is 'in press') have shown no changes in alignment (but we also showed a reduction in the addcutor moment).
Almost all (with a couple of exceptions) of the clinical studies show an improvement in symptoms in those with medial knee OA and lateral wedges (none reported an increase in symptoms).
Foot type does appear to be important - it appears that those who are already at end ROM of STJ benefit most (though evidence points to this, it is limited) (...so wedges do not pronate foot more as its already at end ROM).
The type of wedge does appear to be important - we have a paper in press titled "Length Does Matter" - the adductor moment was most effectively reduced when the wedge extended forward to under the 5th met head.
In all the studies (including the first 110 subjects of our study), there has not been ONE case in which there was any increase in foot symptoms reported.
A problem is the podiatric mindset of "pronation = bad", that we have to get over.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
You are right we have to think out of pronation=bad. I believe when we put a valgus wedge, especially when you put it from the rearfoot till just before CM5 that you will decrease the adductor moment of the tibia and so opening the medial side of the knee. So for a certain amount of patient this will work and yes especially when they have used there complete pronation STJ ROM because then you don't increase tibial endorotation and have maximal impact on the adduction tibial moment. But with patients were you increase STJ pronation and where the femur exorotates, will give no release and will gives over time more problems? Maybe I have to try a valgus wedge with one of these patient and see what happens.
How many of the subjects has no decrease in pain??? What was the degree of the valgus wedges??
lateral wedging for medial knee OA...like many goodthings in life, there goes a saying, "don't knock it if you haven't tried it...." do try it.
At the PFOLA conference a few weeks ago in Chicago there were serval speakers who'd done research on wedging and bracing for medial knee OA. Having my notes at the office and me being at home, I must apologize for not being able to say who they were, however, in one particvular study where some patients were given bracing for agiven period of time, then a rest period to let thier knee "go back to the untreated level" and then given a lateral wedged orthotic, the patients had better results in terms of pain releif, I belive, than those with the brace. It was added that the brace was harder to use as well. I believe the valgus wedge was roughly 4-5 degrees from heel to the toes. Perhasp someone who has thier notes with them can give a more accurate account of this.
Here is abstract of one of the preliminary projects we did - the full publication is 'in press': Laterally Wedged Insoles in Knee Osteoarthritis: What are their Immediate Clinical and Biomechanical Effects and can they Predict 3-month Clinical Outcome?
Rana S Hinman, Kim L Bennell, Craig Payne, Ben R Metcalf
Quote:
Objective:
To assess i) immediate effects of laterally wedged insoles on walking pain, external knee adduction moment and knee alignment and; ii) whether changes in these parameters with insoles, as well as age, body mass index and disease severity, predict clinical outcome after 3 months of treatment in medial knee osteoarthritis (OA).
Methods:
Forty community volunteers (mean age 64.7 yr, 16 male) participated. Participants were tested with and without a pair of 5 degree full length laterally wedged insoles in random order. Immediate changes in static knee alignment were measured via the mechanical axis on radiograph. Changes in adduction moment were measured via 3D gait analysis. After 3 months of treatment with the insoles, changes in pain and physical function were assessed via the WOMAC index and patient-perceived global change scores.
Results:
Reductions in all measured parameters of the adduction moment occurred with insoles (p<0.01), accompanied by a reduction in walking pain of approximately 24% (p<0.01). Insoles had no mean effect on alignment. Mean improvement in WOMAC pain (p=0.004) and physical function (p=0.016) was observed at 3 months, with 69% (25/36) and 72% (26/36) of people reporting a global improvement in pain and function respectively. Regression analyses demonstrated that age, disease severity and magnitude of immediate change in i) walking pain; ii) alignment and; iii) the first peak adduction moment with insoles were predictive of clinical outcome at 3 months.
Conclusions:
Laterally wedged insoles immediately reduced the knee adduction moment and walking pain but had no mean effect on knee alignment. Although some parameters were found to predict clinical outcome these explained only a quarter of the variance in outcome, suggesting that other unknown factors are also important.
Although some parameters were found to predict clinical outcome these explained only a quarter of the variance in outcome - one of these was a greater amount of rearfoot eversion (ie STJ was probably at end ROM).
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
Using radiographs of the knee to assess the biomechanical effects of valgus shoe wedges for the treatment of medial knee osteoarthritis (OA) really does not make good biomechanical sense. As I have said before, and I will keep saying it again and again, the valgus shoe wedge does not need to cause a "opening up of the medial joint space" or a "widened medial joint space" for it to also be therapeutically effective at the knee joint. If the valgus shoe wedge significantly decreases the external knee adduction moment, then it will likely relieve some medial knee OA symptoms, without a concomitant change in radiographic appearance of the knee.
Using radiographs to assess how in-shoe wedging mechanically affects the intracompartmental pressure at the knee makes about as much mechanical sense as using lateral radiographs of the foot to assess how accommodative orthoses might relieve plantar pressures in diabetic patient with plantar foot ulcers. Does the plantar foot no longer touch the ground when accommodative orthoses are placed under the foot (i.e. does the orthosis "open up the plantar foot-floor space"??) or, more correctly, do these orthoses cause decreased force per unit area (i.e. pressure)?
In much the same way, static radiographic assessment of the knee joint spaces does not tell us whether there has been a change in the intracompartmental force per unit area (i.e. pressure) within the knee. Therefore, since pressure [pressure is measured in the same units as stress, force per unit area] is probably the mechanical factor which is actually responsible for the pain of medial knee OA, why even take knee films other than to assess actual remaining joint space in each knee compartment and to assess the overall frontal plane aligment of the hip, knee and foot for possible surgical treatment?
Again, for those that don't understand the mechanical logic behind this, please go back to Thought Experiment #7 for a review of these important concepts.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
hello Freeman,
I didn't say that I don't use valgus wedges for medial knee OA. I just use a valgus wedge for a few patients with specific (mis)aligment (if we can use the word "mis") in relation with there gait pattern. I would never use it on patient that I have explained before (STJ pronation in combination with knee exorotation, so torsion around the knee). But because of the results of the study on pain relief mentioned before (Craig) I was prepared to chalange my brain. Even I am not convinced it will work with this patients because the torsion will be still the same and even get worser, but I believe that a valgus wedge will change something in the joint not on the angle but on the compression in the joint??? (reduce adduction knee moment). SO I find it worth to try. Of course when my initial treatment doesn't work well, so no patient rabits.
So my goal was to chalange others to look not only at the knee and foot but also higher and to think about what a valgus wedge will do to the other structures and will cause other complains. But I have chalange myself too, so good job.
The study that you have mentioned was the one of Hillstrom. He had looked at the effect of valgus knee bracing and neutral position foot orthoses for varus knee OA. So one group only used the braces and the other group both the brace and NPFO. And they came to the conclusion that the combination of bracing and NPFO was more effective. So they didn't use valgus weged foot orthosis.
Background: Radiographic measures of lower limb malalignment are used to indicate abnormal loading of the knee and to plan corrective procedures.
Hypotheses: Weightbearing status during hip-to-ankle radiographs will significantly affect malalignment measures; malalignment in single-limb standing will be most highly correlated to the external knee adduction moment during gait, a proposed dynamic measure of functional knee joint load.
Study Design: Controlled laboratory study.
Methods: Mechanical axis angle was measured in 40 patients with varus gonarthrosis from hip-to-ankle radiographs taken with patients in single-limb standing, double-limb standing, and supine positions. Kinematic and kinetic data were collected during walking and used to calculate the peak adduction moment about the knee.
Results: Repeated-measures analysis of variance and Scheffé post hoc tests indicated that mechanical axis angle measured on single-limb standing radiographs (–8.7° ± 4.0°) was significantly greater than on double-limb standing radiographs (–7.1° ± 3.8°), which was significantly greater than on supine radiographs (–5.5° ± 2.8°). The peak knee adduction moment (2.8 ± 0.8 percentage body weight x height) was only moderately correlated with mechanical axis angle on single-limb standing (r = –0.46), double-limb standing (r = –0.45), and supine (r = –0.43) radiographs.
Conclusion: Patient position significantly affects frontal plane knee alignment. However, the peak knee adduction moment is only moderately correlated to mechanical axis angle, regardless of weightbearing status.
Clinical Relevance: These findings are inconsistent with the hypothesis that mechanical axis angle measured in single-limb standing is more representative of dynamic joint load and further highlight the differences between static and dynamic measures. Results also underscore the importance of reporting patient position during radiographs and keeping positions consistent when evaluating patients over time
I hear that one of the major running shoe companies has an experimental shoe in development that has a higher density EVA under the lateral side and a softer EVA under the medial side (ie the opposite of the 'motion control' shoe) aimed to mimic the effect of a lateral wedge. If the shoe goes into production, it would be targeted at the medial knee OA group ....
Here is the run down:
Quote:
But the latest in a series of studies by a different group of Stanford researchers suggests that a variable-stiffness shoe may be a less conspicuous option.
The experimental shoe, which is being manufactured by Nike for the purposes of the current research and may ultimately be marketed by the athletic shoe giant, features a sole that is 2.5 times more rigid on the lateral side than on the medial side. On the strength of previous research in which the experimental shoe was associated with decreased peak knee adduction moments in healthy subjects, the investigators analyzed its effect on gait in 26 subjects with symptoms of unilateral medial compartment knee OA.
They found that mean peak knee adduction moment was significantly lower while the subjects wore the experimental shoe than when they wore a control shoe (with a homogeneous sole stiffness equal to that of the medial side of the test shoe) or their own personal shoes. The differences between conditions were significant at three different walking speeds, ranging from 1 m/s to 1.7 m/s.
However, the amount of reduction seen in the knee adduction moment varied within the study population, and not all subjects experienced a decrease, said Jennifer Erhart, a graduate student in the department of mechanical engineering, who presented her group's findings at the ASB meeting. For example, at normal walking speed, the change in knee adduction moment ranged from a 20% decrease in one subject to a 7% increase in another; four patients experienced increases.
The results suggest that patients with greater baseline knee adductor moments may benefit most from this type of intervention.
"Individuals with a high knee adductor moment have greater reductions with the intervention shoe," Erhart said. "Gait testing is a good screening tool to identify responders versus nonresponders."
The effect of a subject-specific amount of lateral wedge on knee mechanics in patients with medial knee osteoarthritis.
Butler RJ, Marchesi S, Royer T, Davis IS. J Orthop Res. 2007 Apr 27; [Epub ahead of print]
Quote:
We examined if a subject-specific amount of lateral wedge added to a foot orthosis could alter knee mechanics to potentially reduce the progression of knee osteoarthritis in patients with medial knee osteoarthritis. Twenty individuals with medial knee osteoarthritis (>/=2 Kellgren Lawrence grade) were prescribed a custom laterally wedged foot orthotic device. The prescribed wedge amount was the minimal wedge amount that provided the maximum amount of pain reduction during a lateral step-down test. Following an accommodation period, all subjects returned to the laboratory for a gait analysis. Knee mechanics were collected as the subjects walked at an intentional walking speed. Walking in the laterally wedged orthotic device significantly reduced the peak adduction moment during early stance (p < 0.01) compared to the nonwedged device. Similarly, the wedged orthotic device significantly reduced the knee adduction excursion from heel strike to peak adduction (p < 0.01) compared to the nonwedged device. No differences in the peak adduction moment during propulsion or peak adduction during stance were observed between the orthotic conditions. A subject-specific laterally wedged orthotic device was able to reduce the peak knee adduction moment during early stance, which is thought to be associated with the progression of knee osteoarthritis. Previous studies on this device have reported issues associated with foot discomfort when using wedge amounts >7 degrees; however, no such issues were reported in this study. Therefore, providing a custom laterally wedged orthotic device may potentially increase compliance while still potentially reducing disease progression
Interesting thread which i did not notice first time around. A question springs to mind:-
If valgus wedging decreases compressive forces within the medial compartment of the knee joint does it follow that Varus wedging increases compressive forces in the medial compartment of the knee?
If the answer to the above is yes it raises another question,
Will orthotics which supinate the foot excacerbate / cause medial knee pain and joint degeneration in some cases?
or
Can orthotics which supinate the STJ beyond a certain point (which is probably nothing to do with STJ neutral ) cause medial knee pain / joint damage.
The implications of these questions are substantial. Anyone got some answers?
Interesting thread which i did not notice first time around. A question springs to mind:-
If valgus wedging decreases compressive forces within the medial compartment of the knee joint does it follow that Varus wedging increases compressive forces in the medial compartment of the knee?
My belief is no. If you use varus wedging (ie a foot orthotic), you tend to get external leg rotation (because of the range of STJ inversion most people have) and no (or minimal) change in frontal plane moments at the knee. If you use a valgus/lateral wedge, the STJ goes to end range of eversion easily (and in the case of most in the age group we are talking about, the STJ is already at end ROM), so we get no or very minimal change in tibial rotation, but there will be changes in frontal plane moments at the knee. What limited data is available supports this.
I in the middle of preparing powerpoint on some of our data for a conference next week.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
so when my interpretation is right, you are saying that there is a correlation between age and maximal eversion in the subtalair joint, so the older the more eversion???
Most of those who we recruit into our knee OA studies have very limited or no eversion available from RCSP - all are >50yrs. When the lateral wedge them is used, we see no changes in alginment, but changes in kinetics.
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
Interesting thread which i did not notice first time around. A question springs to mind:-
If valgus wedging decreases compressive forces within the medial compartment of the knee joint does it follow that Varus wedging increases compressive forces in the medial compartment of the knee?
Unquestionably yes.
But that doesn't mean that we suddenly become fearful of increasing compressive forces in the medial compartments of all knees.
In healthy subjects without knee osteoarthritis, the peak knee adduction moment influences the acute effect of shoe interventions designed to reduce medial compartment knee load.
Fisher DS, Dyrby CO, Mundermann A, Morag E, Andriacchi TP. J Orthop Res. 2007 Apr;25(4):540-6.
Quote:
The purpose of this study was to evaluate shoe sole material stiffness changes and angle changes that are intended to reduce the peak knee adduction moment during walking. Fourteen physically active adults were tested wearing their personal shoes (control) and five intervention pairs, two with stiffness variations, two with angle variations, and a placebo shoe. The intervention shoes were evaluated based on how much they reduced the peak knee adduction moment compared to the control shoe. An ANOVA test was used to detect differences between interventions. Linear regression analysis was used to determine a relationship between the magnitude of the knee adduction moment prior to intervention and the effectiveness of the intervention in reducing the peak knee adduction moment. Peak knee adduction moments were reduced for the altered stiffness and altered angle shoes (p < 0.010), but not for the placebo shoe (p = 0.363). Additionally, linear regression analysis showed that subjects with higher knee adduction moments prior to intervention had larger reductions in the peak knee adduction moment (p < 0.010). These results demonstrate that shoe sole stiffness and angle interventions can be used to reduce the peak knee adduction moment and that subjects with initially higher peak knee adduction moments have higher reductions in their peak knee adduction moments.
Hello Graig,
So one of the inclusion criteria was that they have in stance position a limited eversion mobility? Which makes a great difference because then you have more influence on the adduction moment of the knee, but is this a representative population??
It was not an inclusion criteria - its just that all of the subjects are >50 years and in that age group the range of eversion is limited (mnay had no eversion from RCSP).
__________________ Craig Payne
__________________________________________________ ___________________________________ Follow me on Twitter | Run Junkie God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
If valgus wedging decreases compressive forces within the medial compartment of the knee joint does it follow that Varus wedging increases compressive forces in the medial compartment of the knee?
Craig said
Quote:
My belief is no
Atlas Said
Quote:
Unquestionably yes.
Hmmmm. Vive la difference.
Atlas also said
Quote:
But that doesn't mean that we suddenly become fearful of increasing compressive forces in the medial compartments of all knees.
Where is the emphasis in that sentance? Is it the word "all"? As it we should be fearful of increasing the compressive force in some knees?
I'll put it another way. If you have a patient with little or no eversion available from RSCP, who has a pathology which it seems likely is caused by this (lets say a functional HL or a fascitis) and who has medial knee pain caused by compressive OA would you still use a supinating orthotic to treat the foot pain?
Robert
Maybe a slight deviation from your question but is our orthotic intervention only affecting one plane or is the composite effect on all three planes giving us the desired outcome at the local level of the foot?
I believe that a significant amount of the positive orthotic interaction is to accelerate/decelerate the CoP/CoM. If we reduce the amount of time spent at intial contact, will the destructive force caused by the adductor moments associated with intial contact be alterted? Consequently the potential for increasing the adductor moments assocaited with medial compartment OA will be negated or reduced.
I am waffling a bit(!) but I think that the phasic timing of gait is extermely important and is effected by orthoses but we are still struggling to measure this due to individual reactions to the orthoses.
I presume by Accelleration /decelleration of COM COP you are referring to gait analysis with F scan or similar and that cool little Dot which wanders up the foot on playback (or i may have misunderstood you completely).
For the benefit of those of us who only have a passing aquaintance with this technology would you mind elaborating on the "initial contact" bit. From my technologically challanged persperctive i would have thought "initial contact" is the moment the foot hits dirt. How can you spend more or less time doing this?
I tend to agree that what you call "phasic timing of gait" is of vital import and is an oft overlooked aspect of orthotic design. Probably because its a little too easy to see the patient standing still and imagine that that is the whole story.
Regards
Robert
(I put a bid in for an F scan to carry out better gait analysis. They offered me a broom to sweep the bit of corridor i walk people up and down on instead. NHS <> Money = Blood<>Stone)
Robert
Glad that deviation is good - it will give Cameron something to add to his sex therapy courses!!
Yes I was refering to the F-Scan dot thing - I love it and use it in an NHS clinic - I am a very lucky boy.
My thoughts on intial contact being variable are based on some work I have been doing on footwear adaptions. Using SACH and striker heel mods to the heel of footwear, I have been attempting to increase the duration of heel contact and to consequently reduce plantarflexion moments at the ankle.
I am making large assumptions as I am 'defining' the intial period as the 1st 10-15% of the CoP info that I am getting from the F-Scan in shoe system.
This is all based on trying to reduce forefoot pressure in the diabetic foot by reducing plantarflexion moments at intial contact. It seems to be a good theory but needs a lot more research - I am hoping to do it soon but a 4 month baby at home has cramped by style a bit.
You lucky dog! Who did you have to kill to get that kind of hardwear!?!?
That sounds like an interesting idea but theres a lot i don't understand about it. For one thing how will reducing PF moments at initial contact affect forefoot pressure. Forefoot's not on the ground at initial contact! I can see how delaying forefoot contact might reduce the impulse at forefoot load areas, is that what you mean? The other thing which springs to mind is that forefoot pressure is a somewhat vague idea. Are we talking peak pressure, impulse, total presure?
Interesting stuff, might be worth cracking off a new thread if you are so minded. Or we could just wait for your research. I won't hold my breath. My daughter is now 8 months old and i'm starting to think we've bred the world first nocturnal Baby. The idea of working when i could be sleeping is anathema!
The idea started as an attempt to treat the neuropathic diabetic foot. There are a few articles (Sorry I havn't got the references to hand) that showed that as neuropthy increases, one of the 1st muscle groups to be effected is the tib ant = reduced dorsiflexion force available. Secondly the glycosilation of the tendons - especially the TA- led to increased stiffness in the TA and increased plantarflexory force. The CoP was seen - subjectively in my patients - to accelerate anterioly faster than non-neruo feet with increased duration of loading times on the forefoot. This seemed to translate into higher forefoot pressure but more importantly, increased duration of load at the met heads.
Therefore the idea is to slow down the CoP at 'initial' contact, decrease the early loading of the forefoot and reduce impulse at the forefoot.
Subjectively this seems to be working but I am finding that rocker soles and other footwear mods are better at producing the right results than FFO's alone. Combined Footwear and FFo's seems the 'gold' standard but I am a million miles away from being able to say this with any confidence.
) cause medial knee pain / joint damage.
NHS <> Money = Blood<>Stone)
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