Dismay when reading recent paper on lateral heel wedge treatment for knee OA

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Does anyone else feel vexed about the lack of biomechanical knowledge even in research? I was recently reading an article about the use of lateral rearfoot wedges in (mostly medial) knee OA and the Authors completely ignored biomechanical factors instead saying the treatment looks like it may be more effective in women and increased effectiveness in reducing the amount of knee adduction in OA clients with weight and other demographics. This was to me (and probably many other pods) pretty woeful as I would only ever use a lateral wedge to treat med knee OA when the OA has progressed the knee to genu valgum and rearfoot valgus otherwise the rearfoot lateral wedge would create compensationary pronation and therefore more knee internal rotation or where there is no compensationary pronation available just more knee adduction.
I wonder with this and other research, that did include measurement of foot posture index, that basic biomechanical knowledge isnt taught anymore in favour of the more trendy biomechanical theories

 

Hi Louise,

Your comments are right on! Using a lateral heel wedge to treat medial knee OA is medical misfeasance, to say the least, and in my opinion, malpractice.

 

I am quite vexed about lack of biomechanical knowledge. Which bits of knowledge are you referring to. Are you familiar with the mechanical concepts of moment, force couple and free body diagram analysis? These mechanical concepts can be, and are applied to the structures of the foot.

 

The simple mechanics of the foot allow for medial wedge correction of rearfoot varus to prevent pronatory compensation requirement to bring down the forefoot any lateral wedge will increase need for pronation and therefore internal knee rotation or where there is limited stjt compensation available the lateral wedge in a neutral or varus rearfoot will increase knee adduction but it will help where the knee OA has progressed to the stage of genu and rearfoot valgus as is often the case with knee OA.

 

When I say it will help..it may or may not but shouldn't make the pathology worse where the OA has progressed to genu and rearfoot valgum.

 

Anyway I'm just trying to say that its not rocket science and I don't think it serves anyone to no longer have the basics...

 

Hi Louise,
You and I might disagree on what the basics are. There are some very old ideas proposed by Isaac Newton that are the basics I think people should have. There are some new fangled ideas that came out in the 1950's and 1960's that are really confusing people about how the foot works. These new fangled ideas like neutral position of the subtalar joint, compensation for a "deformity", and unlocking of a foot are all ideas that have lead away from the basics and have created confusion. Unfortunately, some of these later ideas are still being taught in podiatric education. To understand how the foot moves you need to understand mechanics (forces and moments and not just positions or shapes).

 

I haven't studied the new website theories but it always made sense to me that in a rearfoot varus where there is stjt rom a medial wedge can remove some of the compensation needed by the stjt for the fft to reach the ground. Just makes sense as does the increase need for such stjt movement when the fft is taken further from the ground as with a lateral wedge. Stjt pronation we were taught causes internal knee rotation maybe the new theories disprove this so I apologise but yet I wouldn't put a lateral wedge where there is knee OA where it has not progressed to a genu valgum deformity and I see this often.

 

Maybe you can explain to me why you would put in a medial antipronatory orthotic if not to reduce pronation compensation required to bring down the forefoot in a rearfoot varus.

 

I agree that you should add a varus forefoot wedge when the foot in resting stance does not bear significant weight on the medial column. This foot is at the end of range of motion of the STJ and cannot evert any farther and the medial column is up in the air.

Now there is a foot that when placed in subtalar joint neutral position, the medial forefoot is up in the air. When allowed to pronate the medial column can bear weight. Some would say that this "compensation" away from neutral position is a problem. But, it is not. Neutral position is a theoretical normal, with no real good explanation of why being in this position should be ideal or normal. Once the medial forefoot reaches the ground there is no more "compensation demand." There is a big difference between looking at just the position of the foot versus looking at the external and internal forces on the foot.

Why do you think pronation compensation is bad?

 

I think that adding extra pronation compensation requirement in knee OA (by adding a lateral heel wedge when its not reached genu and therefore rft valgus) will just increase internal knee rotation and that adding more compensation requirement where there is no stjt compensation available will create increased knee adduction. Is it that you are saying that these are beneficial movements created by the lateral heel wedge intervention? -as even the recent paper that I read was citing knee adduction as a force to be avoided in medial knee OA.

 

It took 20 years of denial before other research teams validated Rothbarts foot (i.e., medial column supinatus).
I wonder how long it will take for the biomechanical model to be discarded as fatally flawed, and the Neurophysiological (foot) model to be embraced. Until then, all this mechanical dialogue will continue.

 

I agree that a lateral wedge should not be used in the presence of genu valgum, and when there is no pronation range of motion available. However, in the presence of genu varum and medial knee compartment arthritis the forefoot valgus wedge would be beneficial. With genu varum there is a tendency to increased medial knee compartment forces and valgus wedges have been shown to decrease adduction moment on the tibia which would decrease medial compartment of the knee forces. Also valgus wedges have been shown to decrease tension in the plantar fascia. One of the most satisfying treatments is to give someone with peroneal tendonitis a valgus wedge and at the first step they go ow wow, that's better.

The above can be easily explained by understanding the forces involved. It is important to look at the forces that cause the motion and not just the motion.

Why do you think subtalar joint pronation and internal knee rotation are bad?

 

I wasn't referring to bad and have not mentioned 'bad' at all and wasn't talking about anything other than knee OA. I just a was wondering why you believe an intervention that increases knee internal rotation in medial knee OA (ie where there is rft varum or neutral rft) would be beneficial?

 

Patient complains of medial knee OA. Medial knee OA in the presence of genu varum, feels better when you decrease external tibial adduction moment. A lateral wedge is beneficial because it decreases external adduction moment. Why would anyone care about internal knee rotation if their knee feels better? Yes, there is a risk of creating sinus tarsi syndrome with a valgus wedge. You should warn the patient that they may get sinus tarsi pain when you give them a valgus wedge. You should also be asking if there are any problems on a follow up visit after you give someone a medial wedge. A medial wedge will increase external tibial adduction moment and could cause medial compartment knee pain.

 

Ok so by what means does it reduce knee adduction in the varus rearfoot? In my mind it could potentially reduce it slightly but would increase it markedly at the end of the gait cycle to allow the forefoot to reach the ground.

 

Also I'm still not sure how internal rotation of the knee could be beneficial to knee OA (ie when there is a lateral heel wedge added the extra compensation requirement catered for by stjt pronation in rft varus and neutral rft).

 

Also I feel like this lateral heel wedge is just asking a lot in terms of first met dorsiflexion. Do we have a bit (maybe) of a less sore knee but a lovely new HAV?

 

Draw a lower leg and foot in a knee with genu varum. Free body diagram analysis. Downward body weight is applied to the top of the tibia and upward ground reaction force is applied to the bottom of the foot. With genu varum these forces will not be directly aligned and thus will create a force couple that will create an adduction moment on the lower leg. The magnitude of the moment is proportional to the distance between these two forces. A valgus wedge under the foot will tend to shift the upward force under the foot more laterally and this would more closely align body weight and reduce the adduction moment on the lower leg.

Are you talking about a compensated or a partially compensated rearfoot varus?

 

I never said internal rotation of the tibia was beneficial. Why would pronation compensation at the STJ affect the knee?

 

HAV is caused by high loads under the first metatarsal. A valgus wedge will tend to decrease loads on the first met head.

 

I'm not saying a lateral rearfoot wedge in rearfoot varus will directly dorsiflex the 1st excessively but the ground ceratinly will and then likely failure of windlass etc...

 

I would say that this is the same with the neutral rft with a lateral heel wedge. The ground dorsiflexes the 1st too much ans again the only time I would use it would be in genu and rft valgum where the deformity is what causes the excessive 1st dorsiflexion by the ground and the wedge doesnt increase this but instead provides a more laterally stable limb.

 

This is the first time I have read you acknowledging the existence of medial column supinatus, which is the hallmark of Rothbarts Foot. I find this amazing since you have denied the existence of this foot structure for over 20 years!

 

Embryological studies on the human fetus are conclusive: Rearfoot varus is a theoretical construct. Possibly, it might occur postpartum, resulting from catastrophic trauma.

It is time to put that term to rest.

 

Why not valgum too? And we can just say were all the same physically...how nice

 

If our human foetus is the model of the fully developed physical skeleton then blow me down with a feather!

 

I suppose that puberty then also as not present in the foetus...is just a fabricated concept that doesn't exist...please let it also be true for menopause!

 

Could it be that the rft varus is only observed with ground contact and the position present in response to the ground...if only we could just float around the womb all day as we do in Podiatry!

 

Sorry that was harsh.

 

J have to say I'm flabbergasted by this. When I think of even a new born foot there is no MLA - is it that there never is then? I really hope this foetal fact didn't contribute to pod students today not learning the basics.

 

Rearfoot Valgum is also a theoretical construct introduced by Root nearly 80 years ago. It does not exist as an embryological structure.

Click on the link (in italics) above. It provides a concise review of the fetal stages in the development of the human foot.

 

So are you contesting that all human development post embryo is merely theoretical? And therefore as all newborn children are born with flat feet there therefore is no such thing as a medial longitudinal arch anywhere but in the minds of theorists?

 

Anyway...here is the google answer...
normal babies do they have flat feet. Yes, it is completely normal for babies to have flat feet. Almost all infants are born with flat feet, largely because a protective layer of baby fat (the plantar fat pad) hides their developing arches.Why Babies Have Flat FeetBaby Fat Pads: Infants have a thick layer of fat on the bottom of their feet that cushions their steps and obscures the arch.Loose Joints: Babies and toddlers have more flexible ligaments and joints. When they stand or walk, their body weight causes the feet to flatten out completely.When Do Arches Develop?Arches do not form immediately; they begin to emerge gradually between the ages of 2 and 6 as muscles and bones mature.

 

Never said that.

Never said that.

Never said that.

 

Brian, Root Orien, and Weed made a definition and then described some measurements that would fit that definition. Are you familiar with the measurements they described? Are you saying that if you were to do those measurements on a person that you would not find someone who fit their definition of a rearfoot varus? Their description of the behavior of a rearfoot varus exactly matches your description of the foot type you named after yourself without crediting them. Plagiarism.

 

I didn't think that could be what was being suggested. I am just wondering why the basics are no longer taught? I just find that they give such a good grounding and believe that they should be taught before tissue stress theory.