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?).

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