Lateral Foot Wedge

Lateral wedging, in this context, is the use of some sort of materiel or modification under the lateral or outer side of the foot to try and pronate or evert the foot some more. The effect of this is to provide a moment or force on the lateral side of the subtalar joint axis.

Conditions lateral wedging can be used for

Peroneal tendon pathology:
One of the functions of the peroneal tendons is to evert or pronate the foot. If a foot is easy to supinate (low supination resistance), then the peroneal muscles have to work harder predisposing the athlete to peroneal tendonitis. This often responds really well to the short/medium term use of lateral wedging in the shoe.

Chronic ankle instability:
If the foot is easy to supinate, then it is going to be easy to sprain the ankle laterally. People with lower supination resistance often describe ‘going over’ on their ankle frequently. This study confirms that impression and supports the use of lateral wedging to reduce the risk of ankle instability. They are not going to be able to control the position of the foot up in the air off the ground, but they will be effective at reducing the supination or inversion tendency when the foot is on the ground.

Medial knee osteoarthritis:
Lateral wedging has been demonstrated in many studies to reduce the knee adduction moment at the knee in those with medial compartment knee osteoarthritis (OA) leading to previous recommendations to use lateral foot wedging for medial knee OA. An increase in this knee joint moment is a significant risk factor for medial knee OA and a predictor of knee OA progression, so that is plausible. However, most of the controlled clinical trails of this have not showed it to be generally helpful, leading its use to be dropped in the clinical guidelines for knee OA.

When you look at the clinical trials, they show that if they are used generally in those with medial knee OA, they do not do much better than a control. However, looking closer at some of the data, some people respond very well to the lateral wedging, some don’t respond and a few get worse, so on average the studies will typically conclude that they are no better than a placebo or control treatment. Research is currently underway to identify what it is about the group that did improve and if the improvement can be predicted by any biomechanical parameters. (See the personal opinion below on this). All the research on this is linked and discussed in this thread on Podiatry Arena on lateral wedging for medial knee OA.

How to make the lateral foot wedge?

There are a number of ways to do this. The aim is to create a lever arm on the lateral side of the subtalar joint axis to alter the kinetics (forces) about that joint. One of the studies showed that a full length lateral wedge was generally more effective than just a heel wedge. This may be because lateral wedging under the forefoot has a bigger lever arm to the subtalar joint compared to just a wedge under the heel.

Commercially available insoles:
There are some commercially available laterally wedged insoles that are on the market. They generally come in different lengths.

EVA lateral foot wedges:
Some suppliers have strips of EVA material that is wedged. They can be cut to the required length and shaped around the heel to fit inside the shoes. These do need to be of a high enough density so that they are just not flattened by body weight and will have no effective on the kinetics if body weight flattens them.

Podiatry Felt/EVA/Cork on insole or in shoe:
There are a number of material, such as self adhesive podiatry felt, an EVA or cork like material that can be cut and adhered or glued into the shoe on the lateral side. The material could also be placed on an over-the-counter insole or orthotic to get the same effect.

Lateral skive/posting on custom made orthotics:
A Kirby or medial heel skive is often used in foot orthotics to apply more force medial to the subtalar joint, so an option for lateral wedging is to use the opposite on the lateral side of the heel, a lateral Kirby skive.

Dual density:
Another option other than wedging is to use dual density material with a softer material on the medial side under the heel and a firmer or harder material on the lateral side. This should get the same effect as a lateral foot wedge. There are a number of patents awarded for the use of this concept in shoes. ASICS for brief time had their ASICS Gel Melbourne shoe that they tested to do just this. I understand that the aim for this shoe was to target the medial knee osteoarthritis market with a walking shoe.

Fitting laterally wedged insoles into footwear

The research linked above showed that a full length lateral foot wedge is more effective than just a lateral heel wedge. It is easier to fit a heel wedge into the shoe, but fitting a full length one can be a bit of a challenge. A full length wedge that goes up under the forefoot and toes might be too much to fit into a particular individual’s shoes. Compromise may be needed. Sports type footwear which already have a removable insole are probably best for this as the insole can be removed and replaced by a full length lateral wedge. The wedge probably does not need to go under the toes and just extend to be under the metatarsal heads.

Personal opinion on lateral foot wedges

I have been involved in my fair share of research on the use of lateral wedging (eg see here and here) as well as using it a lot clinically when indicated. When first exposed to the concept, I just said ‘no way’ as the mindset at that time was that ‘overpronation‘ was the root of all evil and doing anything that pronates the foot some more is going to be a really bad thing to do. With greater understanding of the biomechanics (especially the concept of supination resistance and the understanding of posture or alignment vs forces or kinetics) involved and not seeing any issues in the research that we were doing and with them clinically, I became more and more comfortable doing it when indicated. I have no problems it doing in those that need it. There is still some ideological opposition to using it by some people, but the number that think that way is declining.

The first time I used lateral wedging many years ago was in a case of resistant peroneal tendonitis in a runner; nothing was helping. They had an ‘overpronated’ foot and foot orthotics to stop that was not helping. Changing running shoes was not helping. Physical therapy and exercises were not helping. Modifying the training routines was not helping. This was about the time that we were starting to become aware of the concept of supination resistance. I was becoming aware of use of lateral wedging in those with low supination resistance. So, in act of ‘we have run out of options’ I gave it a go. To our amazement, the clinical response was dramatic and almost instantaneous. There was obviously something to this and I went from there.

I have never had any concerns about lateral wedging causing other symptoms except in those, perhaps, with a higher supination resistance which you probably would not be using lateral wedging anyway. Just like any intervention in the shoes, a bit of time may be needed to get used to wearing them and should start with small does and build up from there so the body can get used to it.

Use in medial knee osteoarthritis:
See above for the status of the research on this. Despite the clinical guidelines about not using them for this, I still do use them at times. They are simple and cheap compared to other interventions for medial knee OA. Yes, they do appear to help some people and, yes, there are some they do not help. I get the impression (and its not backed by any research) that those with a more limited eversion range of motion available when standing or a more rigid foot is more likely to be helped at the knee by the lateral foot wedging. Lateral wedging is going to have two different effects in those who have a range of eversion available at the subtalar joint versus those who are already at the end range of motion. A simple test I use clinically is get them to do a squat standing on and off a lateral wedge and see how that affects the pain in the knee. If the pain is reduced or feels better, then it worth giving it a go.

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