Lateral foot wedging for medial knee OA

Thank you for all your help Kevin.

 

The knee joint axis is fighting the abduction moment?

The big picture questions:

Does this pain relief cause damage to the other joints affected by pronation thus causing more problems than it solves?

If this is damaging to other joints are not the various knee braces altering alignments doing the similar damage?

Are we tinkering with beautiful alignments that are not open to this type of intervention?

I can't answer these questions due to my practice interruptions.

Are the "medications" of orthotics so potent that they are like drugs and need to be prescribed only by physicians with a standard of care? Like drugs some are OTC and some Rx are the consequences so involved that only physicians should be prescribing orthotics or certain types of orthotics.

I consider Biomechanics harder than surgery should there be a separate board for this intervention noting that this field is only going to progress from FES to robotics? Is mixing orthopedics with medicine board mixing things to complex to do both?

Like the role of the pharmacist in medicine should the pedorthist handle the prescription with the same exactitude as the pharmacist?

Will the role of the pedorthist become like the pharmacist a doctorate?

 

An axis is an imaginary line and cannot create moments. In genu varum, when you load from above and below the forces applied will tend to increase the varum deformity or that could be stated as an increased adduction moment on the tibia. When there is an adduction moment on the tibia it will adduct unless something prevents it. The force couple of downward force from the femur applied to the medial side of the tibial plateu and tension in the lateral ligaments will prevent the adduction of the tibia.

I've told this story before on the arena. I've got a pateint with sinus tarsi pain and medial knee pain. The first orthotic relieved his sinus tarsi pain (medial skive) and created knee pain. I shaved a little off the plantar medial rearfoot post, then a little more. His knee pain went away. A couple of months later he's back with sinus tarsi pain and knee does not hurt. I have him tape a coin to the underside of the medial edge of the orthtic to invert it a little more. Two weeks later he comes back and nothing hurts....... Remove the coin.....put it back....

I'm pretty sure I know how orthotics work. However, there are a lot of other people who are quite sure how orthotics work. I disagree with their theories. So, how do we decide who's right so that they can be the only ones who an dispense custom orthotics.

I guess the analogy is to medications where the mechanism of action is not known. We, as the health professional have to evaluate our treatment and alter the treatment based on results.

Eric

 

Effect of footwear on the external knee adduction moment - A systematic review.
Radzimski AO, Mündermann A, Sole G.
Knee. 2011 Jul 4. [Epub ahead of print]

 

In-shoe plantar pressure measurements for patients with knee osteoarthritis: Reliability and effects of lateral heel wedges.
Leitch KM, Birmingham TB, Jones IC, Giffin JR, Jenkyn TR
Gait Posture. 2011 Jul 6;

 

Lateral wedge insoles for medial knee osteoarthritis: Effects on lower limb frontal plane biomechanics.
Hinman RS, Bowles KA, Metcalf BB, Wrigley TV, Bennell KL
Clin Biomech (Bristol, Avon). 2011 Aug 19;

 

My observation based on having been assigned to adapt insoles until the muscles worked correctly.
Those adapting with the plantaris and/or planterflexing the hallux benefited from lateral wedges.
Those with Morton foot or chronic fore foot abduction did not benefit but did benefit with a flat lift under the distal first metatarsal. not a wedge which caused sliding rather than ground force contact. According to instruction from Rothbart height was determined by palpation of the tarsals resting square on the calcaneus. Height was adjusted as muscles strengthened and balanced.

 

HansMassage:

You just lost all your credibility with me by mentioning the word "Rothbart" to describe anything to do with foot biomechanics. Just thought you should know that I am probably not the only one here that shares my thoughts in this regard. :butcher::bang::craig:

 

Hi there

Could someone please try and help me conceptualize how we get external adduction moments and internal abduction moments at the knee. I understand how using valgus wedging is able to shift the CoP laterally because I can visualize this concept in the frontal plane but how do adduction and abduction moments occur at the knee joint?

Regards

Daniel

 

Hi Danial,

It's helpful to think in terms of the force couples created and using free body diagrams. Take a leg with genu varum. Now just look at the foot and leg below the knee. The force from the body above (gravity acting on the body) will be lateral to the force from the ground on the bottom of the foot. (Draw this in the frontal plane.) These two forces will attempt to rotate the bottom of the tibia toward the midline. This is a knee adduction moment. I don't really like talking about internal and external, but would rather talk about the moment from one source versus the moment from another source. So the moment just described has to be countered to maintain equilibrium. We know it's in equilibrium because the knee will not be rotating when the person with genu varum is standing in static stance. So there has to be a moment from some other source, to maintain equilibrium. This can come from compression force on the medial side of the knee. Specifically, the force from the medial condyle of the femur applied to the top of the medial side of the tibia. The other force is tension in the lateral colateral lateral ligament of the knee. (The lateral collateral ligament applies an upward force on the tibia.) These two forces will create a force couple that will tend to rotate the bottom of the tibia away from the midline of the body. Both of these moments exist simultaneously. They are equal and opposite reactions.

The shifting of the center of pressure will change the lever arm of the force couple. And this is how the moment changes.

I hope this helps.

Eric

 

Hi Eric

Thanks for your explanation, its helped clarify things a lot. I have a couple of questions below:

Is the force from the body lateral due to the bodies CoM shifting laterally?

So this would be defined as the internal abduction moment then?

Regards

Daniel

 

No the bodies center of mass can be in between the feet with a genu varum. However, the top of the tiba will be lateral to the bottom of the tibia because of the angle of the leg that is genu varum. What I did in the free body diagram analysis was to isolate the lower leg, remove the rest of the body and look at the forces applied to the lower leg. Two of those forces are: the doward weight of the body that the tibia is supporting, and the upward force from the ground applied to the foot. The center of mass of the body does not apply a force to the top of the tibia. The bottom of the femur applies a force to the top of the tibia.

One of the difficulties in using the terms internal and external is that it has to be internal or external to an arbitrarily defined system. When I defined my "system" as the lower leg, both of those forces are external to the system.

When results of knee adduction moment are reported, they are implying the "system" is the entire lower leg. So, the forces applied to the entire lower leg are the force from the body applied to the top of the femur and ground reaction force at the bottom of the foot. With genu varum these external forces will create an external adduction moment at the knee as they are external to the system. The tension in the lateral collateral ligaments and increased compression at the medial side of the knee are the internal forces that create the internal abduction moment. The internal abduction moment is equal and opposite to the external adduction moment.

This is why I don't really like the use of internal and external. You cannot calculate the magnitude of the knee moment unless you change your system to just the upper or lower leg as opposed to using the whole leg. Ideally, in mechanics, you describe the moment applied by one part to another part.

The difficulty that comes from the definition of the system was solved well in David Winter's articles and books. It's interesting to look at his diagrams and descriptions in relation to joint moments, because he usually works around this confusion very well.

Eric

 

Daniel:

I like the concept of internal and external moments when I lecture and teach biomechanics. I find this type of terminology can be helpful in explaining how frontal plane moments are produced at the knee joint and especially can help in understanding the results from recent experiments where frontal plane knee moments are derived using inverse dynamics. In most biomechanics research using inverse dynamics, joint moments are reported as internal moments, not external moments.

If a valgus wedge under the foot shifts the center of pressure (CoP) laterally, then there will be an increase in external knee abduction moment. Now, if this valgus wedge doesn't increase the abduction motion of the knee, then, by the laws of rotational equilibrium, we know that must be some equal and opposite moment preventing the knee from abducting. Therefore, this equal and opposite moment, caused by the pulling of the ligaments around and in the knee and the change in joint compression forces due to the valgus wedge, is an internal knee adduction moment.

If a varus wedge under the foot shifts the center of pressure (CoP) medially, then there will be an increase in external knee adduction moment. Now, if this varus wedge doesn't increase the adduction motion of the knee, then, by the laws of rotational equilibrium, we know that must be some equal and opposite moment preventing the knee from adducting. Therefore, this equal and opposite moment, caused by the pulling of the ligaments around and in the knee and the change in joint compression forces due to the varus wedge, is an internal knee abduction moment.

The illustration below should help with this explanation. LCCF-lateral knee compartment compression force, MCCF-medial knee compartment compression force, LKTF-lateral knee tensile force

 

Eric and Kevin:

Thanks again as always. I'm understanding this subject a lot more clearly now.

Daniel

 

Daniel:

Just to clarify, in the illustration I provided to you yesterday, the internal moments at the knee which I have included in my example are three separate internal forces:

1. Lateral knee compartment compression force which causes an internal knee adduction moment.

2. Medial knee compartment compression force which causes an internal knee abduction moment.

3. Lateral knee tensile force from lateral collateral ligament, biceps femoris muscle and iliotibial band which creates an internal knee abduction moment.

In my simplified example, I have left out other possible important contributors to internal knee moments such as the medial collateral ligament and sartorius, gracilis, semitendinosus, and semimembranosus muscles medially which all will create an internal knee adduction moment.

The external knee adduction moment in my example comes the ground reaction force vector (acting on the plantar foot) being located medial to the anterior-posterior axis of the knee.

Hope that further clarifies this illustration I provided yesterday that I use for one of my lectures on knee osteoarthritis and treatment of knee OA with foot orthoses.

 

Hi

I have of late had a look at some of the literature on this subject. Im coming away with the feeling that lateral wedging does change knee moments which should change knee compressive forces. However clinical RCT's seem to be suggesting a lack of effectiveness ie in practice it doesnt work to reduce pain in knee OA.

I believe that Craig Payne has only recently published a study that came up with no improvement compared to the control group.

Anyone know of anything to change this opinion????

 

There was an interesting presentation from Peter Cavanagh at the ISB mtg in South Africa 2 yrs ago (I think it was that mtg!). He did a bit of a beat up on the biomechanists. For eg he talked about all the studies on how much pressure reduction occurred with a particular diabetic insole or shoe and the claims were made from that about the reduction in ulcer that would occur ... but the research was never taken through to clinical trials to see if that was actually the case or not.

The parallel here is the data on lateral wedging for medial knee OA.
1) Risk factor studies have shown a higher external adduction moment at the knee is a significant predictor of knee OA and a significant predictor of its progression
2) All (or almost all) lab based kinetic studies have shown a reduction in that moment with lateral wedging
3) Therefore this should help knee OA (see the parallels above with diabetic pressures and insoles/shoes eg)

When this gets taken through to the clinical trial, GENERALLY the uncontrolled trials show they work; the controlled studies with weaker methodology GENERALLY show they work. The one study we did that was well resourced, well controlled etc etc showed they did no better than the control group (though both groups improved equally)..... herein is the dilemma; what do we do with this information? There are several more well controlled RCT's on this underway....do we wait? Do we act on this info now?

 

The answer for me is easy on this one. I have been using valgus rearfoot and forefoot wedging for my patients with medial knee OA for 20+ years with good success for mild to moderate cases of medial knee OA. I will continue to do so regardless of what the research says. I pity the clinician that feels that they need to wait for "definitive research" to know what to do for their patients. Why wouldn't you use these wedges? They are cheap, have virtually no side effects, and if they do cause problems, then you take them out of the shoe...no harm done.

 

Wonderful thread..I would agree and add only this:
I have done many as well and the lateral wedge for us is our starting point to treatment of medial knee OA. The wedge progression is relative to the degree of medial offloading required for pain management and yes it is subjective. Once this fails to reasonably resolve the pain then the use of a medial compartment unloader is used as a next step. The whole idea is to keep a patient yet determined as too young for replacement sugery off the table for as long as you can. Sometimes they have to wait and they want pain relif and mobility. Sometimes the wedge was all they needed at all for many years. Each progression is different.

Thankyou

 

Thanks Kevin, Craig and Todd

I not a evidence-slave! Its just that with this therapy the evidence is beginningg to suggest no clinical effect. This is not the same as no evidence!

I guess the question, Kevin, is what are you doing the researchers are not, or how are you measuring your outcome, compared to how they are measuring their's. Is it just a case that your patients wear their orthoses and those in the study dont?!

Lawrence

 

Lawrence:

Here is how I measure the outcomes: I put the wedge in their shoe, they return in two weeks and say they can't believe that something so simple hasn't been tried before by their other doctors and they want more wedges added to their other shoes. Generally their pain isn't completely better, but it is a signficant decrease in pain in over 75% of cases. By the way, the valgus wedge must be under both the forefoot and rearfoot in order to get these results and some patients require more of a wedge than other patients.

I initially use multiple layers of 1/8" adhesive felt in their shoe or on their insole on the initial fitting . On the first fitting, I keep adding valgus wedging until they feel noticeable relief in their medial knee when walking for a minute in my office. Possibly the researchers are using too little of a wedge to notice an improvement?

 

Kevin

Maybe it comes down to the fact that you apply the felt until you get the feedback from the patient on symptom relief. Perhaps this leads to a variability in the amount of wedging that leads to success and a strict RCT protocol can't replicate that.

Lawrence

 

Lawrence:

And this is the exact problem with the type of study that uses a "standardized valgus wedge" for the treatment of medial knee OA and, also, is the same problem with many foot orthosis studies that use only one type of foot orthosis for all subjects in the study....this is simply not the way that an experienced and talented clinician treats their patients in a real world clinical situation in an attempt to achieve optimal treatment results.

 

Kevin do you add lateral flares to the shoes to aid the patient with lateral wedges?

And what do you think are the nuances of this treatment?

 

Also Kevin would not medial flares and laterally worn shoes be problematic for the patient.

 

Also if the lateral flare is softer than the medial flare then you have created a medial wedge.

 

Kevin, Craig

Maybe whats needed is a "experimentum crucis" as Newton would say!

Maybe a better protocol would be to decide what reduction in Knee moment is required then set a study protocol that will achieve this for each participent. Thus to achieve a 20% reduction in the knee moments in all individuals a 3, 5 or 8 degree valgus wedge may be needed. Rather than setting a pre-detirmined amount of posting. Then compare this orthotic to a control group.

This reflects what Simon Spooner was talking about at the Biomechanics Summer School, studies should be carried out with the posting applied according to the amount of moment they change rather than the degree, angle or millimetres. This because of the amount of variation in individual responses.

 

Kevin, Thus for people who use shoes with medial wedges that are causing varus knee angulation as a secondary effect for trying to control pronation may account for the epidemic of knee medial knee OA.

Lawrence Bevan, an 8 degree wedge would probably make you slide off the wedge unless you use the Kirby felt method which might be preventing slippage due to compression and friction.

 

Nope. The evidence from Nigg et al and one other that I can't recall at the moment is that there are non-systematic effects on adduction moments at the knee from "medial" foot orthoses. In other words they decreased the moment in half the subjects and increased the moment in the other half. SO, yes there is a theoretical increased adduction moment in ~50% of those that use foot orthotics, and, yes, that would theoretically lead to an increased risk for medial knee OA. BUT that needs to be interpreted in the context of:
1. The risk is theoretical and no clinical trial has demonstrated it
2. It only happens in ~50% with an improvement in the other 50%
3. If no other risk factors for knee OA are present (eg obesity; hereditary;trauma), then a small increase in the adduction moment is hardly going to be a problem
4. Its also going to depend on the severity of the symptoms that the foot orthotics are designed to treat.

 

Conclusion Lateral wedge insoles worn for 12 months provided no symptomatic or structural benefits compared with flat control insoles.

Research
Lateral wedge insoles for medial knee osteoarthritis: 12 month randomised controlled trial
OPEN ACCESS
Kim L Bennell, professor1, Kelly-Ann Bowles, research scientist1, Craig Payne, senior lecturer2, Flavia Cicuttini, professor3, Elizabeth Williamson, postdoctoral fellow34, Andrew Forbes, professor3, Fahad Hanna, postdoctoral fellow35, Miranda Davies-Tuck, postdoctoral fellow3, Anthony Harris, professor6, Rana S Hinman, associate professor1

 

Discussed earlier in this thread. ie the wedge group actually did get better, but so did the control group; study did not address subject specific responses; the intervention was standardized vs subject specific; etc etc ..

 

from the American Academy of Orthopedic Surgeons’ Full Guideline for the Treatment of Knee Osteoarthritis.
Recommendation 8 – Lateral heel wedges are not recommended as a treatment option for osteoarthritis of the knee.

 

What about the two national rheumatology organizations that do recommend it as part of their guideline?. You also need to read about what led to the AAOS recommendation (it was based on the lack of evidence at a certain level to support it, not on evidence that it did not work). You not going to do yourself any favors by cherry picking.

 

Ok, can someone just give me the podiatry cookbook so I can look up the recipe!

 

Lawrence:

I believe your idea of variable thickness valgus wedges (both rearfoot and forefoot valgus wedges) is a sound one. This is how we do it in the clinic, why not treat subjects experimentally just like we do in the clinic?

 

Joe:

I don't know if there is any more incidence of medial knee OA now than there was years ago. Certainly any varus wedged orthoses could exacerbate medial knee OA pain, but I have never seen orthoses cause the onset of medial knee OA in a knee that is otherwise non-pathological.

 

End of conclusion states, "However, given the clear biomechanical benefits
of wedge insoles in reducing medial knee load, further research is needed over a longer time frame to conclusively determine the effects of lateral wedge insoles on
joint structure."

 

Sorry my net connection has been mucking up and i missed a lot of posts before i posted so please ignore, mark

 

If obesity is a risk factor for Medial OA why wouldn't increase load from an anti-pronator shoe be a risk factor? One of my techniques for diagnosis is to stick an imaginary pin into the foot to diagnosis structures along the way, now a days I turn the pin around and start at the skin going through the sock, orthotic, shoe materials and enviornment to help diagnose. Shoes are not easy. I think all the sports specific shoes are being misused in leisure sports. I no longer believe a good running shoe is a good walking shoe for the reasons I mentioned earlier.

 

Knee OA incidence rates rose 22% from 1990 to 2005 and are rising even faster than obesity rates.

Knee OA and obesity: A cyclical clinical challenge


Obesity not only increases the risk of knee osteoarthritis but also makes it more difficult to treat, as typical exercise recommendations often are simply not practical. Gait researchers, however, are working to identify new potential therapeutic approaches.

by Elizabeth M. Russell, MS, and Joseph Hamill, PhD