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Craig:

Sorry, I misread your original statement and agree that your original statement makes sense to me now. What was I thinking?!

Yes, I believe this is the same phenomenon that Root et al described as an accommodative contracture of the gastrocnemius-soleus muscles that leads to an equinus deformity. Muscles that are not placed on stretch on a regular basis will tend to shorten over time.

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

I think that this is the primary focus. You want to minimise pathological forces including pathological compensation mechanisms.
For any biomechanical problem, there are likely many factors involved. I feel the biggest error we can make is to not, at very least, consider all these factors.
You summed it up well I think-
Although I would have probably also used the term - 'provide an appropriate degree of supination force early on rearfoot loading'-
Put simply-
1-decrease the ankle equinus as much as possible (stretching, soft tissue therapy etc)
2- provide resistance against the pathological forces which are caused by the equinus in a way that does no harm to foot function and is comfortable for the patient. (orthotic with appropriate control, often with a heel lift initially)
3- On review assess the effectiveness of the plan!
This is all doing what you said- allowing the foot to develope optimally- I like the word 'optimal'- I use it a lot

__________________
Craig Tanner
Podiatrist
ASPETAR-
Qatar Orthopaedic and Sports Medicine Hospital
Doha
QATAR
http://www.aspetar.com/

Eric originally wronte

I have a problem with the idea that midfoot flexibility will cause an equinous. The reasoning above seems to be saying that if they get the dorsiflexion at the midfoot they will not use the ankle dorsiflexion and therefore loose the ankle dorsiflexion. Again we should look at stiffness to test this idea. The stiffness of the ankle joint is quite variable. In the middle of the range of motion, if there is little tension in the Achilles tendon (from muscle contracture) then the ankle will be very flexible. When the ankle joint dorsiflexes to the point where there is passive tension in the muscles attaching to the Achilles tendon then the ankle joint will be a lot more stiff.
CraigT responded

Eric Responds
I agree that there are several things that can contribute to ankle joint stiffness. However something causes the stiffness of the joint to increase as you go from plantarflexion to dorsiflexion. That something can be substituted in the argument below.

Eric orignally wrote:

So when the ankle joint is in the middle of its range of motion and the forefoot is dorsiflexed on the rearfoot to the point where the plantar ligaments are tight the midfoot will be more rigid than the ankle joint and force applied to the forefoot would tend to dorsiflex the ankle joint over the midfoot in this situation.


I think we start running into a measurement problem when you use the above hypotheticals. When measuring ankle joint dorsiflexion you apply force to the forefoot to dorsiflex the ankle and then look at the angle between the weight bearing surface of the foot and the leg. In this position the forefoot is already maximally dorsiflexed. (Or dorsiflexed until stiff) How do you measure forefoot dorsiflexion independently of ankle dorsiflexion?

I would certainly agree that there will be variability across individuals in maximum stiffness and the amount of range of motion available with low stiffness. However, the measurement tecnique for ankle range of motion is measuring the midfoot in the position where it has high stiffness in the direction of dorsiflexion.

Let me restate your question. Look at the sagittal view angle between the plantar surface of the calcaneus and he cuboid. Dorsiflex the fifth metatarsal until you feel the stiffness of the fifth met cuboid joint increase and then measure the angle. Let's say the two lines are parallel. Now an injury occurs to the foot and you perform the same measurement and you see the metatarsal line is 5 degrees dorsiflexed relative to the plantar suface of the cuboid and calcaneus. I think this what you are trying to say above. Let's say that when the ankle joint is dorsiflexed to a point where you feel stiffness the angle between the plantar surface of the calcaneus and cuboid is perpendicular to the leg. So, before the injury, when the leg to the ground measurement (sagittal plane) passes past perpendicular the heel will begin to lift and the forefoot will theoretically pivot about the fifth meatarsal head. After the injury, at the same point in gait the rearfoot will pivot at the distal aspect of the cuboid until the slack of the plantar ligaments is taken up (probably 5 degrees) and then it will pivot about the metatarsal heads. When the foot pivots about the distal end of the cuboid there is still a dorsiflexion moment at the ankle jont from ground reaction force at the distal end of the cuboid. This dorsiflexion moment could prevent an ankle equinous from developing.

In the above foot that is injured there may be a pain avoidance response where the person refrains from using the gastroc and soleus muscles and in this situation the equinous would not develop because the gastroc and soleus are contracting less and would tend to not develop a contracture.

Well, that's a lot of arm chair theorizing.

Eric

I rember being taught flatfoot leads to equinus as well. It was another one of those ideas that I had a hard time accepting the first time that I heard it. I'm not sure that I accept it now.

Cheers,

Eric

Eric,
This is an interesting hypothetical!
Referring back to what I described earlier-

Often when doing this test, patients will have a dramatic difference in dorsiflexion, or effort required for the same amount of dorsiflexion, when the 1st MTPJ is dorsiflexed.
When an individual requires a certain amount of dorsiflexion during gait, then they are surely going to use the mechanism which offers the least amount of resistance.
This is what I am I am referring to in this hypothetical.
I may not be understanding you correctly, but I think you are saying that the dorsiflexion moment will still be applied and therefore resist the equinus.
Do you think it is possible that the application of this dorsiflexion moment could be delayed by the midfoot flexibility? If this is the case, could the firing of the gastroch/soleus stiffening the ankle joint come into the picture?? This would then increase the plantarflexion moment... ?something else to consider.
Maybe a research project in this..? -please, my well read colleagues, jump in and list previous studies here...
Cheers

__________________
Craig Tanner
Podiatrist
ASPETAR-
Qatar Orthopaedic and Sports Medicine Hospital
Doha
QATAR
http://www.aspetar.com/

Eric:

I don't have a hard time accepting this idea since it seems to correlate with my clinical observations. I do believe that age has an effect in the sense that it is much more common to see flatfoot in adults associated with equinus than to see flatfoot in children associated with equinus. I commonly see children with pes planovalgus deformity with very large ranges of ankle joint dorsiflexion whereas rarely see adults with pes planovalgus deformity with normal ranges of ankle joint dorsiflexion. We know that muscles will accommodate to a shorter length over time if not stretched regularly. Possibly these accommodative shortenings of muscles require years in some people and only months in others? It makes good sense to me that a plantarflexed rearfoot due to a pes planovalgus deformity over time will cause accommodative shortening of the gastrocnemius-soleus-Achilles tendon complex just as women with a habit of wearing high heeled shoes for most of their lives will develop a limitation in ankle joint dorsiflexion as they age.

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

Part of our problem here in this discussion is that we all need to realize that our current definitions and terminology for ankle joint dorsiflexion and for determining whether an "ankle equinus deformity" is present or not is inherently flawed. We must understand that dorsiflexion of the forefoot on the rearfoot will not only affect our measurement of the kinematics and kinetics of the midtarsal/midfoot, but will also affect our measurement of the kinematics and kinetics of the ankle joint. In other words, when we are saying "ankle joint dorsiflexion", what we are really saying is "midtarsal/midfoot dorsiflexion and ankle joint dorsiflexion".

In other words, if the midtarsal/midfoot joints have increased dorsiflexion motion or increased dorsiflexion stiffness, then we will measure increased ankle joint dorsiflexion motion and increased ankle joint dorsiflexion stiffness, assuming all other things are equal. If the midtarsal/midfoot joints have decreased dorsiflexion motion or decreased dorsiflexion stiffness, then we will measure decreased ankle joint dorsiflexion motion and decreased ankle joint dorsiflexion stiffness.

So, as walking gait progresses during midstance, if the midtarsal joint has decreased dorsiflexion stiffness, that lack of forefoot dorsiflexion stiffness will delay the increase in ankle joint dorsiflexion moment that occurs since the intrinsic reduction in forefoot dorsiflexion stiffness will directly affect the transmission of dorsiflexion moments to the ankle joint. In other words, if the plantar forefoot is too flexible to bear the weight from the ground, then ankle joint dorsiflexion moments from ground reaction force (GRF) will be greatly reduced since ankle joint dorsiflexion moments, by definition, require GRFs distal to the ankle joint axis (i.e. plantar to the forefoot) to be present.

If, however, there is increased forefoot dorsiflexion stiffness, then ankle joint dorsiflexion moments will be rapidly increased as midstance progresses due to the rapid increase in GRF plantar to the forefoot. Therefore, midtarsal/midfoot dorsiflexion stiffness is not only a consideration when determining ankle joint dorsiflexion stiffness but is, by our current definitions, a mechanically important factor that determines ankle joint dorsiflexion stiffness.

All of these factors I have presented above are also affected by any ankle joint plantarflexion moments and midtarsal/midfoot plantarflexion moments that are caused by contractile activity of the extrinsic and intrinsic muscles of the foot. These are very complex mechanical interrelationships, but certainly, biomechanical analyses, such as the ones provided in these discussions, will lead us all into a better understanding of the function of the bipedal human organism.

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

Regarding the theory that high midfoot flexibility (low stiffness) leads to contracture of the gastroc soleus compelx.

I agree with the observation that if you don't use it you will lose it. Now the question is whether or not these people lose their ankle range of motion becuase of a flexible midfoot or some other reason. Perhaps the older folks don't run around as much and avoid pain by not stressing their ankle joint range of motion.

Good discussion,

Eric

Lifting the hallux will raise the arch height. As arch height increases the talus will have to dorsiflex to keep the heel on the ground. I beleive Don Green called a cavus foot with limited ankle ROM a pseudo equinus because there was contact of the neck of the talus with the anterior infierior part of the tibia. It was pseudo equinus because the Achilles tendon was not the cause of limited ankle motion. When you raise the arch with the windlass you are creating more of a cavus foot so I would bet that you get a smaller angle (leg to vertical) with your test about 100% of the time.

However, the windlass activiated in this situation is not a normal situation. The forefoot will tend to be maximally dorsiflexed when weight bearing.

The moment is not delayed in time, but, as Kevin described, the moment is smaller. The center of pressure under the foot is closer to the ankle joint in the flexible foot. This moment will still tend to dorsiflex the ankle. An ankle equinous will result if the gastroc and soleus have constant activation to create a plantar flexion moment. If the person is able to relax the gastroc and soleus then the ankle joint will dorsiflex in response to the moment from ground reaction force. You are right the activity of the muscles comes into play. You have to examine the moments from all sources. The problem with these theoretical discussions is we cannot necessarily predict the moment from muscle activiation. The muscle is activated by CNS activity and behavior is hard to predict.

Cheers,
Eric

Could a simple AFO work by creating mild dorsi flexion may well encourage subtle soft tissue flexibility and increase ROM.