When wearing orthotics most weight seems to be on arch of foot

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(New user to podiatry arena here and I'm not a medical professional, please pardon me if my post/question is not appropriate for this forum.)

I have flat feet and hallux valgus and have had orthotics prescribed twice so far. My understanding is that the weight of the foot should be ideally distributed on the foot in a tripod fashion (ball of big toe, heel, ball of little toe). Whenever I wear the orthotics, though, most of my weight seems to rest on the arch of my foot and less on the "tripod" parts of my foot. Is this okay?

Another question: my orthotics raise my arch, but I noticed that the ball of my big toe has trouble making contact with the ground. What does this mean? From random googling, I'm wondering if I have forefoot supinatus or forefoot varus.

thanks for reading!

 

A major cause of flexible flatfeet is the PreClinical Clubfoot deformity. When only an arch support is placed under this foot deformity, it will make it difficult for the 1st metatarsal and hallux to purchase, rest, on the ground.

There are specific proprioceptive insoles dimensioned to stabilize this foot deformity and distribute the weight in a tripod fashion. In a previous thread, I described how to fabricate this insole -
see Design of the Insole to Treat the PreClinical Clubfoot Deformity at https://podiatryarena.com/index.php...at-the-preclinical-clubfoot-deformity.114306/

Standard orthotics should not be used to stabilize this foot deformation.

You can read about the PreClinical Clubfoot Deformity here.

 

The foot tripod model strikes me as a bad one since it excludes the toes. In fact, trying to model the foot without including the toes, to which all the intrinsic foot muscles attach, is ridiculous.

 

The Tripod Index is an excellent weight bearing measurement index which delineates the ideal foot weight bearing distribution – center of the heel, medial edge of the medial sesamoid and the lateral edge of the 5th metatarsal head.

Lines AB, AC and AD are drawn (see diagram) are drawn through this 3 points. A positive Tripod Index is where line AD is medial to line AB which indicates abnormal (gravity drive) pronation.

I have used this index frequently in my practice, especially when dealing with the PreClinical Clubfoot Deformity.

For a complete discussion, I would refer you to

Arunakul M, Amendola A, et al 2013. Tripod Index. A New Radiographic Parameter Assessing Foot Alignment. Foot and Ankle International DOI: 10.1177/1071100713488761

 

Are you saying that the "ideal foot weight bearing distribution" does not involve the toes? Or met heads 2,3.4 ?

 

Arunakul et al say very little about the phalanges participating in weight bearing during static stance.

50 plus years of clinical experience treating feet, I agree with Arunakul. Static weight bearing, most of the forefoot load is on the 1st and 5th metatarsal heads. This changes in gait. At toe off the hallux participates in weight bearing (in a plantargrade foot).

 

There is one school of thought where that is what is supposed to happen. However the medial arch is not really a weight bearing area and I've had a lot of patients who have not liked the orthotic because of pain in the arch. In my opinion, the ideal weight bearing pattern would spread the force out over as much area as possible. Problems occur when there is too much pressure in one location.

Orthotics should solve the problem that you are having and not create another problem. When an orthotic's arch is so high that you can't bear weight on your heel and your first metatarsal head then this is likely to cause problems somewhere else. Forefoot varus, forefoot supinatus, or any other name of an inverted foot deformity is just some measurement that is not necessarily predictive of pathology. Pathology is an anatomical structure that hurts.

 

Static stance is rare . Most people standing in one spot for any time will tend to shift weight from one side to the other.

IMO , small amounts of pressure under the toes will tend to shift COG significantly back towards the heel , reducing strain in the plantar tissues that span the medial arch.


The following piece of research needs to be done : Find out if toe press exercises change pressure distribution during standing tasks. The implications for health and industry could be enormous.

 

The Tripod Index can be used in different ways. I used this Index as a means to radiographically diagnose gravity drive pronation. There are other non radiographical tests one can use to diagnose gravity drive pronation. For example the Knee Bend Test is an excellent clinical tool which visualizes the timing of gravity drive pronation.

I did not use the Tripod Index for the dimensioning of the proprioceptive insoles. So whether the weight shifted from one side to the other, or from the forefoot to rearfoot, was not an issue.

 

My language was ambiguous ; "one side to another" should read "one foot to another" . If pressure under the toes in single leg stance has no place in your models then I see little use for them.

Painful feet from standing all day is a serious occupational problem for many. However, even just a little additional pressure under the hallux would probably make a big difference to the stress the plantar tissues are subjected to, not by supporting the arch, but by moving the COG and COP proximally ( towards the heel) and laterally. Luke Kelly did some work which touches on this some time ago, but, IMO, misinterpreted the results, possibly because he and his colleagues did not factor in ground reaction forces generated under the toes.

 

[QUOTE="scotfoot, post: 422128, member: 15859 If pressure under the toes in single leg stance has no place in your models then I see little use for them. [/QUOTE]

Please elaborate.

 

Thanks for your reply! I would say most of the weight is on my arch and my heel, with very little on my first met head. Any insights?

 

Decreased load on the first met should reduce symptoms of hallux valgus. It won't reduce the existing deformity. If the decreased load on the first metatarsal is increasing load too much somewhere else, that could cause a problem. If it does you should go back to the person who gave you the orthotics and explain to them the problem you are having.