…. say what? This study, that I will get to eventually, gives me the opportunity to address an issue I have been wanting to get to for a while, so the appearance of the research was timely. The issues surrounding forefoot varus and forefoot supinatus, even just not only on the terminology, but the diagnosis and use of foot orthotics for them is extraordinarily confused leading to flawed and nonsensical conclusions from research. Apologies if this does bore some readers, but hopefully those that it is aimed at get it and understand it!
Forefoot varus and supinatus are constructs that had there original textbook definitions, but those original definitions and (mis)understandings have erroneously morphed over time. Firstly, some definitions of what we are talking about, so at least we talking about the same thing:
- this was originally defined as a deviation of the forefoot in the frontal plane in which the forefoot is inverted relative to the rearfoot when the subtalar joint is in its neutral position AND the midtarsal joint is maximally pronated by loading the lateral column of the forefoot
- the later part of that definition (ie loading the lateral column) is often not done in research studies and by clinicians determining the forefoot to rearfoot relationship. This will lead to a very much higher prevalence of forefoot varus. For example, Garbalosa et al found a prevalence of over 80% when not loading the lateral forefoot (ie not using the textbook definition of what a forefoot varus was). In a study we did, we found the prevalence in the population we looked at that it was only 1.6% by loading the lateral column (ie applying the original textbook definition). I often roll my eye when I see the inclusion criteria for a study as being ‘forefoot varus’ and they manged to find, for eg, 30 people. I always wonder how they determined it was really a forefoot varus and how many 1000’s of people that had to screen to find that 30!
- the textbook definition of forefoot varus is that it is an osseous problem in the head and neck of the talus. However, there are studies by Lufler et al and McPoil et al who dissected cadavers to look at the forefoot to rearfoot relationship and concluded that ‘forefoot varus’ was not bony and was soft tissue. Unfortunately, they were probably looking at forefoot supinatus (see below) feet and not a true forefoot varus. They just called it a forefoot varus as the forefoot was inverted and they did not load the lateral column and they did not distinguish between the osseus inverted position (forefoot vaurus) or the soft tissue inverted position (forefoot supinatus).
- a forefoot varus causes the foot to pronate excessively (ie ‘overpronation’) provided there is a range of motion at the subtalar joint to allow it to pronate. This is what the textbooks would call a compensated forefoot varus (some call this a ‘flexible forefoot varus’ – I wish they wouldn’t). The reason that the foot ‘overpronates’ is that the medial column of the foot has to get down to the ground. We can’t walk or run if it was up in the air!
- there is only one way to stop the ‘overpronation’ from a true forefoot varus and that is with foot orthotics with the right design features – that is assuming that the forces associated with it are high enough to cause tissue damage and foot orthotics are indicated. There is no other way. No amount of barefoot running, gluteal contraction, muscle strengthening, firing of the intrinsic muscles or motion control features in running shoes are going to stop it. The problem is osseous or bony and that medial side of the forefoot has to get down to the ground.
- this is also a position in which the forefoot is inverted relative to a neutral rearfoot when the lateral column of the forefoot is loaded; in other words it looks the same as a forefoot varus
- the difference is that a forefoot supinatus is defined as a soft tissue contracture and is NOT osseous (though to complicate things most forefoot varus’s that I see do have an element of supinatus superimposed on it)
- I would estimate the prevalence of a true forefoot supinatus as being around 20-30% of forefoot to rearfoot relationships (and a true forefoot varus at around 1-2%)
- the cause of a forefoot supinatus is probably two fold:
- 1) when the rearfoot ‘overpronates’, the forefoot can’t go through the ground, so the forefoot is relatively supinated or inverted relative to the rearfoot. Over time, the soft tissue contract and adapt to this position, so that when you put the rearfoot in it neutral position and load the lateral forefoot, the forefoot is going to be inverted relative to the rearfoot. There are many different potential casues of that rearfoot ‘overpronation’
- 2) If the windlass mechanism is not working properly, then when the forefoot is loaded, there is probably going to be some dorsiflexion of the medial column of the forefoot as there is no plantarflexory force coming from the windlass mechanism. Over time, the soft tissues are going to adapt to the dorsiflexed medial column position, creating an inverted forefoot; ie a forefoot supinatus
- in the Garbalosa et al, Lufler et al and McPoil et al studies linked above this is what they were looking at rather than a true forefoot varus (though Garbalosa et al did not even load the lateral column). These studies have been used to debunk the whole concept of forefoot varus, when they weren’t really even looking at it.
- a good way to distinguish between the two is have the person stand; place the subtalar joint in neutral and keep it there; and then push down on the medial forefoot. The supinatus is correctable and a varus won’t be.
- as this is a soft tissue contracture due to the windlass not working or ‘overpronation’ of the rearfoot, this is correctable. Muscles strengthening, contracting the gluts, barefoot running, activating the foot ‘core’, manipulation and mobilization etc can potentially correct this depending on exactly what is causing it (though I still not sure how you actually activate the ‘foot core’!). Even a motion control feature of a running shoe can help this if it can stop what is causing the rearfoot ‘overpronation’ can be affected by those design features – the shoe can affect some causes of ‘overpronation’ and not others
- foot orthotics can help as long as they have the design features that are aimed at the cause of the rearfoot overpronation and facilitating the windlass mechanism AND allow the medial column of the forefoot to come down. A foot orthotic for forefoot supinatus that has forefoot varus design features (ie medial forefoot posting) is going to be an epic fail. Can you see why I roll my eyes when I read foot orthotic studies that recruited 30 people with “forefoot varus” and then used a medial forefoot posted orthotic? They all probably had a forefoot supinatus, making the conclusions from the research of not much use.
- I previously discussed some of the pathomechanics of forefoot supintus being possibly the reason some barefoot/minimalist runners see an increase in arch height and others don’t.
- some people call a ‘forefoot supinatus’ a ‘flexible forefoot varus’. I wish they wouldn’t as others call a ‘flexible forefoot varus’ as a true forefoot varus with a flexible subtalar joint to allow the rearfoot to pronate to compensate for it.
Still with me? To further complicate all this, some lump both forefoot varus and supinatus under the term ‘forefoot invertus’, though that this mostly only in the UK and its fortunately not spreading anywhere else.
In summary: both look the same, but they are totally different beasts:
- a forefoot varus is bony and a forefoot supinatus is soft tissue
- a forefoot varus is a cause of ‘overpronation’ and a forefoot supinatus is the result of ‘overpronation’
- a forefoot varus is rare and a forefoot supintus is common
- a forefoot varus cannot be corrected and a forefoot supinatus can be corrected
Regardless of if you want to disagree or agree with me on the terminology, these two pathomechanical entities exist and are two totally different beasts even if they look the same.
Now to the study in question:
The effects of forefoot varus on hip and knee kinematics during single-leg squat
Rodrigo Scattone Silva, Carlos D. Maciel, Fábio V. Serrão
Manual Therapy; July 12, 2014
Foot misalignments, such as forefoot varus (FV), have been associated with musculoskeletal injuries in the proximal joints of the lower limb. Previous theories suggested that this association occurs because FV influences knee and hip kinematics during closed kinetic chain activities. However, research on the effects of FV in the kinematics of the lower limb is very scarce. Therefore, the purpose of this study was to compare the knee and hip kinematics between subjects with and without FV during a functional weight-bearing activity. Forty-six healthy adolescents were divided into two groups: group of subjects with FV (VG, n = 23) and group of subjects with aligned forefoot (CG, n = 23). A kinematic evaluation was conducted while the subjects performed a single-leg squat task. The variables of interest were hip internal rotation and adduction and knee abduction excursions at 15°, 30°, 45° and 60° of knee flexion. Between-group comparisons were performed with multivariate analysis of variance. Results showed that the VG presented greater hip internal rotation when compared with the CG across all evaluated knee flexion angles (P = 0.02–0.0001). No differences between groups were observed in hip adduction or knee abduction (P > 0.05). These results indicate that FV influences the transverse plane hip movement patterns during a functional weight-bearing activity. Considering that excessive hip internal rotation has been associated with knee injuries, these findings might contribute for a better understanding of the link between FV and injuries of the proximal joints of the lower limb.
Hopefully, if you got what I said above, you will know exactly what I am going to say: that was probably NOT a study on forefoot varus and was mostly likely a study on forefoot supinatus. To make it worse, when you read their methods, it appears that they did not load the lateral column before they determined the forefoot to rearfoot relationship!
I have already written too much, so won’t get into the methods and analysis except to say that they managed to conclude that a ‘forefoot varus’ effects knee and hip kinematics (and I agree a true forefoot varus probably does), but as this was probably a study on forefoot supinatus, how do we not know from this study that it was the differences that they found in the hip and knee kinematics that were causing the “overpronation” that resulted in the forefoot supinatus? or how do we know that what was causing the forefoot supinatus was not also what was affecting the knee and hip kinematics?
Hopefully this makes sense.
As always, I go where the evidence takes me until convinced otherwise …. and its time that we should be talking the same language and not mixing up the bony and soft tissue causes of an inverted forefoot.
Scattone Silva, R., Maciel, C., & Serrão, F. (2014). The effects of forefoot varus on hip and knee kinematics during single-leg squat Manual Therapy DOI: 10.1016/j.math.2014.07.001