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?