The all to common case of the Wobbling Hexapod (Tripod) : Is Your Foot hexa/Tripod Stable Enough to Walk or Run without Injury or Problem ?

Note the music we have chosen today. We tried to match the rate of the dancing tibialis anterior tendon to the tempo of the song, just for fun of course. Well, actually, for neurological reasons as well, as with a steady tempo or beat, your nervous system can learn better. Why do you think we teach kids songs to learn (or you can’t get the theme from the “Jetsons” out of your head).

This is a great video. This client has an obvious problem stabilizing the foot tripod during single leg stance as seen here.  There is also evidence of long term tripod problems by the degree of redness and size (although difficult to see on this plane of view) of the medial metatarsophalangeal (MTP) joint (the MPJ or big knuckle joint) just proximal to the big toe.  This is the area of the METatarsal head, the medial aspect of the foot tripod.

As this client moves slowly from stance into a mild single leg squat knee bend the challenges to the foot’s stability, the tripod, become obvious.  Stability is under duress. There is much frontal plane “Checking” or shifting and the tibial and body mass is rocking back and forth on a microscopic level as evidenced by the dancing tibialis tendon at the ankle level.  The medial foot tripod is loading and unloading multiple times a second. 

Is it any shock to you that this person has chronic foot problems which are exacerbated by running ?  Every time this foot hits the ground the foot is trying to find stability. The medial tripod fails and the big knuckle joint (the 1st MPJ or big toe joint) is enlarging from inflammation, uncontrolled loading through the joint, and early cartilage wear and decay, not to mention the knee falling medially to the foot line as well.  Hallux limitus (turf toe) is subclinical at this time, but it is on the menu for a later date. A dorsal crown of osteophytes (the turf toe ridge on the top of the foot) is developing steadily, soon to block out the range necessary for adequate toe off in this client.  And that means a limitation in  hip extension sometime down the road (and premature heel rise……. did you read Wednesday’s blog post on that topic ?).

*addendum:

Take the time to develop the skill. We ask our clients to work on standing with the toes up to find a clean tripod and do some shallow squats working on holding the tripod quietly. Be sure your glutes are in charge, spin of the limb is in part controlled at the core-hip level so that can a primary location to hunt as well. Eventually work into toes pressed flat but be sure the tripod is still valid, esp the medial tripod. Don’t be what Dr. Allen refers to as a “knuckle popper”. No toe curling/hammering either. Keep that glute on. Move the swing leg forward during a lunge, and then behind you during a squat (mimicking early and late midstance phases of gait/running). This will help your brain realize when it needs this stability and it will also act to press you off balance and will make the foot check and challenge. Do this until you feel the foot fatigue on the bottom. Then Stop. Repeat later. If the medial tripod collapses, the knee will drop inwards and excess pronation is inevitable. We modified this with our prescription of the “100 ups”…..combine the two !

Shawn and Ivo … .  comfortably numb.

Once you have been to the Dark Side of the Moon  (and hopefully you didn’t have any Brain Damage) you will know it well and know what to expect when you return again.  Meaning, when you have seen these issues over and over again, hopefully in your daily work if not regularly here at The Gait Guys, you will quickly know what things to assess and look for in your athletes.  And you might just turn into a Pink Floyd fan at the same time, or at least crave some Figgy Pudding (but you have to eat yer’ meat! How can you have any pudding if you don’t eat  yer’ meat?).

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The partial truth about the Foot Tripod. The HEXApod.

The gait guys have talked about the foot tripod for a very long time. But the truth of the matter is that it is really a HEXApod. HEXA means 6. And when the foot is properly orientated and engaged on the ground, the 5 metatarsal heads and the heel should all be engaged with the ground, truly making it an asymmetrical hexapod. In an ideal scenario, the foot would be most stable if it looked like the strange symmetrical hexapod above with the contact points equally distributed around a center point. But that is not the human foot and this version of a hexapod is far simpler and likely inferior to the foot hexapod when human locomotion is to be attempted. The human foot is engineering marvel when it works properly.  

Perhaps the best example of what I mean by the foot being a HEXApod is in the pressure diagram above. In that first picture, on the right of that picture, we see multiple pressure points under the metatarsal heads of the right foot.  Minus the missing 1st metatarsal head pressure point (taken over by increased flexor hallucis longus activity represented by increased pressure at the big toe),  this pretty much confirms that the foot is not a tripod, rather a hexapod. The theory of the tripod, the 1st and 5th metatarsal heads and the heel, is only crudely accurate and honest. In this picture case, this person has increased lateral foot weight bearing (possibly why the 1st MET head pressure is absent) and possibly represented by pressure under the base of the 5 metatarsal. This is not normal for most people and if this person could get the 1st MET head down, they might even have a HEPTApod foot structure because of the 5th metatarsal base presentation (which sometimes represents peroneal muscle weakness). 

Where did we lead you astray after all these years of “tripod” talk ? We have always discussed the foot tripod. We have always discussed the imperative need to keep the limb’s plumb line forces within the area represented by the tripod.  If your forces fall more laterally within the tripod, as in this first discussed picture, one is at increased risk of inversion events and the myriad of compensations within the entire body that will occur to prevent that inversion. So again, why the tripod?  Well, it is easier to understand and it serves our clients well when it comes to finding active foot arch restoration as seen in this video of ours here.  But, the truth of the matter is that all of the metatarsal heads should be on the ground. The 2nd METatarsal is longer, the 3rd a little shorter, and the 4th and 5th even a little short than those. With the 1st MET shorter, these 5 form a kind of parabolic arc if you will. Each metatarsal head still should contact the ground and then each of those metatarsals should be further supported/anchored by their digits (toes) distally.  So the foot is actually more truly a HEXAPOD. Take the old TRIPOD theory we have always spoken about and extend a curved line beyond the forefoot bipod points (1st and 5th metatarsals) to incorporate contact points on the 2, 3 and 4th metatarsal heads. These metatarsals help to form the TRANSVERSE arch of the foot. It is this transverse arch that has given us the easily explainable foot TRIPOD because if a line is drawn between just the shorter 1st and 5th metatarsals, we do not see contact of the 2-4 metatarsal heads when we only look for pressure between these two bipod landmarks, but the obvious truth is that the 2-4 metatarsals are just longer and extend to the ground further out beyond this theoretical line drawn between the 1st and 5th MET heads.   

So, the foot is a HEXAPOD. Make no mistake about it. It is more stable than a tripod because there are more contact points inside the traditionally discussed foot tripod model. And frankly, the tripod theory is just a lie and just too fundamentally simple, unless you are an American 3 toed woodpecker.

Dr. Shawn Allen,     www.doctorallen.co

one of the gait guys

The Gait Guys. Two weeks ago you talked about a dog’s gait, now cockroaches ? Yup, watching nature at work fosters much insight into gait principles.   
  Biomimetics , also known as Bionics, is another name for engineering systems that copy principles found in nature. 
 If you are real gait geeks you have probably seen some of the cool robots inspired after  the insect world. Many of these robots are called hexapods (six legged robots), just like insects. With 6 legs alternating limbs on opposite sides of their exoskeleton (see diagram above) it can provide an  inherently stable tripod mechanism that is effective and  efficient in when it comes to locomotion.  Insects are great models because they have an extremely stable and efficient model of locomotion through something called a tripod gait. We have a video link demonstrating this a little further down.   At any time, cockroaches for example have 3 limbs in contact with a surface.   This tripod structure makes them very stable and mobile. 
 The stability of the hexapod comes from  its ability to establish this gait pattern in which at least  three legs are on the ground at any time.  Just like the 3 legs of a tripod, when they are firmly planted, the platform is very stable.  You will notice from our year of blogging that we continue to talk about the foot tripod, consisting of stability points at the head of the 1st and 5th metatarsals and the heel. These 3 points of stability of the foot are necessary to make up the longitudinal and transverse arches of the foot. Without the ability to anchor these 3 points effectively on the ground the foot becomes unstable and compromised. Hence why we see bunions, hallux valgus, metatarsalgia, abnormal plantar callus patterns as well as various presentations of foot pain in feet that have lost the tripod ability. The key however is then to place, and maintain, the body mass within the confines or borders of the triangle made by joining these 3 tripod points (see the colored area in the diagram above). In humans, if your body mass deviates towards the outside of the tripod, in other words approaching or violating an imaginary line drawn from your 5th metatarsal to the heel (ie. approaching supination), you tip the foot laterally and begin to compromise the anchoring of the medial foot tripod (under the 1st metatarsal) and risk formation of bunions and hallux valgus among other functional pathologies of excessive or constant supination. On the other hand, If your body mass approaches or exceeds the arbitrary medial border of the triangle delineated by a line drawn from the head of the metatarsal to the heel  you are considered a possible hyperpronator and all of the functional pathologies that accompany it (ie. plantar fasciitis etc).  Bottom line … a tripod is stable, just stay withing the colored lines.  Note in this cool video (click here)  how clear the 3 pronged tripod engages and how the body mass of the robot stays within the borders of the tripod limbs. In other words, keep your ankle and more specifically the force vector, over your foot tripod (the colored lines),  and most pathology issues will be absent. The closer you get to tipping the tripod, the closer  you are getting to developing biomechanical pathology in the lower limb.  Put another way, by increasing weaknesses in the foot intrinsic and extrinsic muscles and possibly the other stabilizers of the lower limb and pelvis, the closer your body mass will fall towards the edges/limits of the tripod triangle borders. And the closer you are to the risk of gait pathology and pain. 
 ( In the diagram above, for you hexapod insect loving gait fans, the most basic hexapod walking pattern is called the  alternating tripod  gait .  Taken from this site , in this gait, the six legs are treated in two groups of three.   Either group of three is a tripod formed by the front and rear legs of  one side, and the middle leg of the opposite side.  The three component  legs of each tripod are moved as a unit.   As one tripod is lifted, the  other tripod pushes forward.  In this gait it can be helpful to think of  each tripod as a foot and compare it to your own bipedal walking where  as one foot is lifted the other foot pushes forward.)  
 And you still thought we were just your average Gait Guys, didn’t you ?! If it walks, trots, gallops, canters, jumps, runs, jogs or whatever….. we are on top of it.  Yes, even if that means cockroaches ! We are here to stay gang, in 2012 we will begin to execute our plan for intergalactic dominance, gait related only of course. 
 Nerd Shawn & Geek Ivo

The Gait Guys. Two weeks ago you talked about a dog’s gait, now cockroaches ? Yup, watching nature at work fosters much insight into gait principles.

Biomimetics, also known as Bionics, is another name for engineering systems that copy principles found in nature.

If you are real gait geeks you have probably seen some of the cool robots inspired after  the insect world. Many of these robots are called hexapods (six legged robots), just like insects. With 6 legs alternating limbs on opposite sides of their exoskeleton (see diagram above) it can provide an inherently stable tripod mechanism that is effective and efficient in when it comes to locomotion. Insects are great models because they have an extremely stable and efficient model of locomotion through something called a tripod gait. We have a video link demonstrating this a little further down.  At any time, cockroaches for example have 3 limbs in contact with a surface.   This tripod structure makes them very stable and mobile.

The stability of the hexapod comes from its ability to establish this gait pattern in which at least three legs are on the ground at any time. Just like the 3 legs of a tripod, when they are firmly planted, the platform is very stable.  You will notice from our year of blogging that we continue to talk about the foot tripod, consisting of stability points at the head of the 1st and 5th metatarsals and the heel. These 3 points of stability of the foot are necessary to make up the longitudinal and transverse arches of the foot. Without the ability to anchor these 3 points effectively on the ground the foot becomes unstable and compromised. Hence why we see bunions, hallux valgus, metatarsalgia, abnormal plantar callus patterns as well as various presentations of foot pain in feet that have lost the tripod ability. The key however is then to place, and maintain, the body mass within the confines or borders of the triangle made by joining these 3 tripod points (see the colored area in the diagram above). In humans, if your body mass deviates towards the outside of the tripod, in other words approaching or violating an imaginary line drawn from your 5th metatarsal to the heel (ie. approaching supination), you tip the foot laterally and begin to compromise the anchoring of the medial foot tripod (under the 1st metatarsal) and risk formation of bunions and hallux valgus among other functional pathologies of excessive or constant supination. On the other hand, If your body mass approaches or exceeds the arbitrary medial border of the triangle delineated by a line drawn from the head of the metatarsal to the heel  you are considered a possible hyperpronator and all of the functional pathologies that accompany it (ie. plantar fasciitis etc).  Bottom line … a tripod is stable, just stay withing the colored lines. Note in this cool video (click here) how clear the 3 pronged tripod engages and how the body mass of the robot stays within the borders of the tripod limbs. In other words, keep your ankle and more specifically the force vector, over your foot tripod (the colored lines),  and most pathology issues will be absent. The closer you get to tipping the tripod, the closer  you are getting to developing biomechanical pathology in the lower limb.  Put another way, by increasing weaknesses in the foot intrinsic and extrinsic muscles and possibly the other stabilizers of the lower limb and pelvis, the closer your body mass will fall towards the edges/limits of the tripod triangle borders. And the closer you are to the risk of gait pathology and pain.

( In the diagram above, for you hexapod insect loving gait fans, the most basic hexapod walking pattern is called the alternating tripod gait. Taken from this site, in this gait, the six legs are treated in two groups of three. Either group of three is a tripod formed by the front and rear legs of one side, and the middle leg of the opposite side. The three component legs of each tripod are moved as a unit. As one tripod is lifted, the other tripod pushes forward. In this gait it can be helpful to think of each tripod as a foot and compare it to your own bipedal walking where as one foot is lifted the other foot pushes forward.)

And you still thought we were just your average Gait Guys, didn’t you ?! If it walks, trots, gallops, canters, jumps, runs, jogs or whatever….. we are on top of it.  Yes, even if that means cockroaches ! We are here to stay gang, in 2012 we will begin to execute our plan for intergalactic dominance, gait related only of course.

Nerd Shawn & Geek Ivo