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Anterior Cavus

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Asher, Dec 3, 2007.

  1. Asher

    Asher Well-Known Member

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    Hi there

    I’ve been thinking about 'anterior cavus', it’s not something that I hear podiatrists talk about often but I have become aware of it in recent years (never considered it previously) now I see it all the time:( - when the forefoot is plantarflexed relative to the rearfoot. I determine anterior cavus non-weightbearing, it’s easy to see on the lateral aspect of the foot.

    So the anomaly is a midfoot (or does it occur at the MTJ only – I don’t know) anomaly in the medial / lateral axis. It is a morphological anomaly. The stiffness of the midfoot determines whether is it fully compensated or not ie: whether the forefoot dorsiflexion moment is sufficient to actually dorsiflex the forefoot to become on the same plane as the rearfoot – stiffness being related to the ‘give’ in the midfoot ligaments and the degree to which the bony morphology allows joint movement – Does that sound right??

    Depending on the passive stiffness of the midfoot, it is either fully compensated (low midfoot stiffness), partially compensated (medium forefoot stiffness) or uncompensated (high midfoot stiffness) - though it depends on the degree of the forefoot plantarflexion obviously.

    These feet need more ankle joint dorsiflexion (compared to if they didn't have an anterior cavus) for toe clearance in swing and in the uncompensated variety, to allow the body to progress forwards over the plantargrade foot. So there is often a lot of extensor substitution going on. The type that is uncompensated has a normal to high arch contour in spite of a very pronated STJ at stance / gait and /or forefoot pathology. Dorsal midfoot exostoses often occur due to dorsal midfoot interosseus compression.

    I certainly wouldn’t want this foot-type, compensated or not.

    This is certainly an anomaly of the medial - lateral axis of the midfoot (M-L MTJ). My gut tells me, as to whether it becomes compensated or not, is mostly about passive stiffness (ligaments and bony morphology). But the previous discussions tell me that active mediated stiffness is also a factor.

    Unlike muscles that produce FF plantarflexion moments (that have been mentioned previously by Kevin K) trying to hold the arch up, muscles are trying to lower the arch ie: its muscles that produce FF dorsiflexion moments that come into play. I guess that’s the extensor substitution and the tib ant trying to get as much FF dorsiflexion as possible – that we see.

    Thoughts? Just happy to enter into a bit of a discussion about anterior cavus, experiences, treatment.

  2. Admin2

    Admin2 Administrator Staff Member

  3. Griff

    Griff Moderator

    Hi Rebecca,

    I see this foot type alot also, unfortunately each time I take my own socks off! Due to having a quite cavoid and rigid foot type, with marked FF Equninus I have to use most of my ankle (TCJ) dorsiflexion just to get my foot plantigrade.

    This results in having very ROM little left functionally, a problem I find improves with bilateral heel raises. I'm also one of those chaps you'd see with a rolled up towel or weight plate under my heels in the gym whilst doing squats to allow myself to squat lower (essentially 'freeing' up what TCJ ROM I have by putting my foot in a starting position more akin to its anatomical/structural position)

    I tend to use this bilateral heel raise addition on most orthoses I issue to folk with a similar foot type, and if in doubt use a further investigation such as the Lunge test which has obviously been discussed on the forum at length
    Last edited: Dec 4, 2007
  4. Asher

    Asher Well-Known Member

    Hi Ian,

    I also use heel raises for anterior cavus whether it be compensated or uncompensated. I'm not quite sure what you mean by your statement below though:

    Do you use the lunge test to gauge what heel raise height you need? If so, how?

    I was wondering about other prescription variables for anterior cavus. Would contouring under the anterior calcaneus to support the calcaneal inclination angle be indicated? I can't get my head around what's going on at the rearfoot. There are increased forefoot dorsiflexion moments but what sort of moments at the rearfoot? I think rearfoot dorsiflexion moments also due to the tension in the plantarfascia etc as the forefoot dorsiflexes.

    Also, if you're reading Craig Payne, at Bootcamp, in your flow-chart on orthotic decision making, is "functional foot drop" the same as "anterior cavus"? Have I got the wrong term in "anterior cavus"?

  5. Griff

    Griff Moderator

    I think its generally accepted (I'm sure I will bw corrected if I'm wrong) that if the tibia cannot get to about 36-38 degrees then a heel raise is indicated, and usually only 3mm is needed (Ref: C Payne - Podiatry Conference, Harrogate, UK Oct 2007)

    Another prescription modification I tend to also use is a plantar fascial groove, for the reason you note regarding the common finding of anatomical tightness. At the rearfoot I would usually expect to see very little happening (kinematically at least) in this foot type, but I'm certain someone more knowledgable than myself will be along to answer you reagrding the rearfoot moment query!

  6. Asher

    Asher Well-Known Member

    Hi Ian

    I thought maybe you had a way of determining how high the heel raise should be. Actually, I guess it needs to be however high it takes to get the 35-38 degree angle before the heel lifts up??

  7. Griff

    Griff Moderator


    That has been my assumption also yes. I've not found a way of determining it any better than that I'm afraid. The only other factor I tend to consider with regards to heel raise height is the patients footwear which of course will dictate what heights may be accomodated or not.

  8. The concept of midtarsal joint dorsiflexion stiffness can be quite helpful in assessing the biomechanical effects of cavus foot deformity. Basically, what we have called "pes cavus deformity" may also be called "a foot with high forefoot dorsiflexion stiffness" in that a large amount of forefoot dorsiflexion moment is required to dorsiflex the forefoot on the rearfoot in a foot with pes cavus deformity.

    Since the clinical measurement that we currently call "ankle joint dorsiflexion" is actually a combination of dorsiflexion of the rearfoot on the tibia and dorsiflexion of the forefoot on the rearfoot, then, of course, forefoot dorsiflexion stiffness will greatly affect our measurement of "ankle joint dorsiflexion", whether that measurement is done in a non-weightbearing fashion or in a weightbearing fashion, such as in a lunge test. If there is high forefoot dorsiflexion stiffness, then we will measure "decreased ankle joint dorsiflexion" and if there is low forefoot dorsiflexion stiffness, we will measure "increased ankle joint dorsiflexion", even there may have been no change in the relative length-tension characteristics of the Achilles tendon and other ankle joint plantarflexors between these two types of feet.

    I would recommend against using terminology such as "fully compensated", "partially compensated" or "uncompensated" when discussing the load vs deformation characteristics of the forefoot to the rearfoot. Unless the terminology of "compensation" can support numerical quantification, can be precisely defined, and can be made unambiguous, then I am against it. Rebecca, can you precisely define "fully compensated", "partially compensated" and "uncompensated" in regards to the midtarsal joint/midfoot joints?

    Certainly the concept of midtarsal joint dorsiflexion stiffness could be combined with the load vs deformation characteristics of dorsiflexion of the rearfoot on the tibia to come up with a combined measure of not only ankle joint dorsiflexion stiffness but also subtalar joint, midtarsal joint, and midfoot joint dorsiflexion stiffness. This new measurement, which could be called ankle-foot dorsiflexion stiffness could represent a very useful clinical measurement of plantar foot to tibia load vs deformation characteristics and may be predictive of gait function, such as early heel off, late midstance pronation, etc.

    In other words, what we have in the past always called ankle joint dorsiflexion is not "ankle joint dorsiflexion" but rather is a combination of dorsiflexion of the metatarsals on the cuneiforms, dorsiflexion of the cuneiforms on the navicular, dorsiflexion of the metatarsals on the cuboid, dorsiflexion of the navicular on the talus, dorsiflexion of the cuboid on the calcaneus, dorsiflexion of calcaneus on the talus, AND dorsiflexion of the talus on the tibia. Until clinicians and researchers understand this basic fact, we will all be wandering around in a fog trying to understand our clinical and research results in regards to the sagittal plane kinematics and kinetics of the foot and lower extremity of the human locomotor system.
  9. Craig Payne

    Craig Payne Moderator

    No idea! The terminology is interchangable. The standard definistion of a traditional pes cavus is posterior (calc is dorsiflexed); anterior (forefoot is plantarflexed); or global (both). The functional foot drop is taken from a theory in a book by an orthotist (which I forget what it is called and is not handy) in which a functional forefoot drop is the cause of everything :pigs: ... the word functional is there, essentially because it increase the demands on ankle joint ROM during gait
    Just to clarify, that was using the lunge test with orthotics in the shoe .... amazing what that little 3mm can do!
  10. Asher

    Asher Well-Known Member

    thanks for your reply kevin, haven't had a chance to read it properly yet but will tonight.

    with regard to your post craig, it makes me think that when we test things like jacks test and supination resistance and the lunge test, although doing barefoot measures is one thing but most people wear shoes so to me, these measures would mean more if done with a heel raise as per the heel height differential eg 10mm for joggers.

    gotta go

  11. Craig Payne

    Craig Payne Moderator

    Absolutly. Supination resistance go down ~15% with a 10mm heel raise. Timing of windlass onset will be earlier with a heel raise.
  12. Asher

    Asher Well-Known Member

    Roger that.

    I must be thick or something. This is really hard to get my head around. I have been here 2 hrs trying to formulate a post that is coherant (that's a lot of CPD points). A few questions:

    Q1. I wouldn't call a 'fully compensated' or flexible' (don't flog me) anterior cavus a cavus foot. To me a cavus foot has a high arch and the joints are stiff. Is mine an incorrect definition of cavus? Do you class this 'flexible' anterior cavus as pes cavus Kevin?

    Q2. When you say
    I get that, if you are talking about what I call pes cavus (high arch, stiff foot). But what about my 'flexible' anterior cavus where the ligaments are not stiff and allow a lot of FF dorsiflexion? Do you class this 'flexible' anterior cavus as having high FF dorsiflexion stiffness? I would say it had low FF dorsiflexion stiffness.

    I can see how the stiffness concept works for planus arch and cavus arch (in the Midfoot Thread). What I can't get is how the concept applies to what I would have called flexible or fully compensated anterior cavus where the ligaments are not stiff and allow the FF to reach the same plane as the RF (ie: lateral border of foot is flat) with nwb examination. If this foot has a planus arch contour when weightbearing, I would write on my biomechanical assessment form "planus arch" and "low midfoot stiffness", this does not indicate that there is much more FF dorsiflexion movement compared to a regular planus foot with "low midfoot stiffness". To me, the amount that this FF has to dorsiflex just to get to the same plane as the rearfoot , is important.

    Q3. Is there a difference between saying "high forefoot dorsiflexion stiffness" and "high midfoot stiffness to dorsiflexion"?

    Q4. Are you saying Kevin that all cavus feet have high midfoot stiffness and all low arch feet have low midfoot stiffness. Therefore, you can't get a flexible (low stiffness) cavus or a rigid (high stiffness) planus foot?

    Q5. I don't know if a pes cavus is stiff because the ligaments are holding the joints together really tight so they can't move much, or if its a combination of the ligaments and the shape of the joints not allowing much motion. Or is it more about this joint morphology?

    I don't doubt you when you say that the terms fully compensated, partially compensated and uncompensated should not be used. In fact, since you have asked can I define these terms, I would initially have said that:

    Fully compensated = the FF reaches the same plane as the RR
    Partially compensated = the FF goes some way to reaching the same plane as the RR
    Uncompensated = the FF cannot dorsiflex at all

    However, the force applied to determine this is a quick push on the FF while nonweightbearing which I realise would mean little anyway. The partial and uncompensated feet don't stand with their heels in the air, of course the feet are plantargrade.

    BTW Kevin, if I'm not being to forward in asking, how do you record stiffness on you biomechanical assessment? Do you rate is 1-3 or 1-5 or low/mod/high ... ?

    I do apologise for this post, I'm struggling.

  13. Asher

    Asher Well-Known Member

    I have pondered overnight as to why the above is important.

    What I have come up with is it is still important, and rating midfoot stiffness still doesn't indicate a flexible anterior cavus degree of compensation (to use my own words for a sec). What I want to know is how much extra the ankle joint has to dorsiflex in gait.

    What I must consider is that when I examine AJ dorsiflexion, I am actually measuring ankle-foot dorsiflexion stiffness as Kevin has explained.

    So if on my biomechanical assessment form I simply say:

    Anterior cavus: YES
    Midfoot stiffness: ?
    Lunge test / modified lunge test: ? (This test measures AJ dorsiflexion but also how much the FF dorsiflexes at the midfoot, so it is a measure of ankle-foot dorsiflexion stiffness)

    Lets say that stiffness measured '1 or low' and the lunge test measured 38 degrees. This is considered 'normal' for the lunge test. Although 'normal' AJ dorsiflexion, there is a significant amount of dorsiflesion at the midfoot going on to get this normal lunge angle. This is my 'flexible anterior cavus'.

    Lets say that stiffness measured '3 or high' and the lunge test measured 30 degrees. This is less than what is considered 'normal'. The lunge angle is reduced because the midfoot, being stiff, cannot dorsiflex to get the angle any further. This is my 'uncompensated anterior cavus'.

    So in this way, without having to mention 'fully compensated' or 'flexible' etc, I know what's going on in that midfoot.

    Actually, maybe I don't even have to rate midfoot stiffness. The key is realising that the lunge test actually tells you how stiff the midfoot is in combination with AJ limitation ie:ankle-foot dorsiflexion stiffness

    Any thoughts would be appreciated.

  14. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Asher,

    I was just reading through the practical handout we got at bootcamp. The handout indicated that the normal mean value for the lunge test is 45 degrees (Bennell et al.,1998: Pope et al., 1998).

    For the modfied lung test, it indicates that the mean value is 35 degrees (Munteanu et al., 2007).

    I just want to make sure that I'm correct?? And, that I'm interpretating the hand out correctly. So far, I have catergorized pt's who are <45 degrees for the lung test and <35 degrees for the modified, as having increased ankle joint dorsiflexion stiffness.

    Perhaps if Craig Payne is reading he can elaborate on this.


    Last edited: Dec 6, 2007
  15. Rebecca:

    I am having a very difficult time answering all your questions. I saw 35 patients today, have already had dinner and took a nice walk with my lovely wife, and am sitting down to relax a little.....on the computer.:)

    If one were to graph the forefoot load vs the dorsiflexion of the forefoot relative to the rearfoot in the flexible cavus foot vs the rigid cavus foot, the graphs would have quite different shapes. The flexible cavus foot would show large forefoot dorsiflexion motion with little applied load until the plantar ligaments/fascia became loaded and then would show much much less forefoot dorsiflexion with increasing loads. However, the rigid cavus foot would show little forefoot dorsiflexion motion with the initial applied plantar load since it has little range of dorsiflexion of the forefoot to the rearfoot.

    We must be careful in classifying feet as flexible/rigid cavus/planus since we may not be talking exactly about the same things. When I say a flexible cavus foot, I mean that the foot is cavus in nonweightbearing but more normal arched during weightbearing. A rigid cavus foot means that the foot is cavus in structure both nonweightbearing and weightbearing. This is one of the beauties of proposing the measurement of a load vs deformation curve of midtarsal/midfoot joints under dorsiflexion loading conditions. The stiffness of the midtarsal/midfoot joints will be seen to increase with increasing forefoot dorsiflexionm motion due to further tensile force within the plantar ligaments/fascia with increasing arch flattening motion. The stiffness will be seen to increase at different arch heights with different foot types. I have never performed these load vs deformation measurements, but I am currently working with some researchers in Spain who are interested in performing this research for the first time. It should be quite interesting.
  16. Asher

    Asher Well-Known Member

    I'm with you Dan, I am hoping for some clarification here as Craig P has stated many times that the cutoff angle for the lunge test (not modified lunge) is 35 degrees.



    PS: Kevin K, I am doing a lot more reading and learning and less talking at this point! Thanks again.
  17. Craig Payne

    Craig Payne Moderator

    Its like a lot of things, we just do not know for sure, so we have to make a judgement call in the absence of hard data. The prospective injury data and the lunge test was based on the distance from the wall (which I do not like as it does not take into account height), so we started working on 35-38 degrees being normal. In this thread Josh Burns talked about his work and liked 30 degrees as the cut-off.
  18. Rebecca:

    You had many wonderful questions that, I believe, were appreciated by many others who are lurking here on Podiatry Arena. Keep asking questions and, time allowing, I will try to answer them to the best of my ability.

    Have a nice weekend.

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