The Rigid Flat Foot: Do you know what you are actually dealing with ?
In these 5 photos of a client with a flat arch we see some great opportunity to discuss some of the clinical issues and clinical thinking that needs to occur. As usual we write our blog posts on the fly with a principle at hand that we want to drive home, or in this case “into the ground”. There are many more clinical issues with this type of foot and its problems, so today’s list and dialogue is not meant to be exhaustive. But, if you take one thing away from this case, it should be that not all flat feet can take a stability shoe or an orthotic. So, if you are in the mind set that “when it is flat, jack it up (the arch)” and “when it is high (the arch), cushion it” hopefully you will open your eyes a bit to the reality that it just is not that simple. IF you want to learn more about these issues we have purposefully put together the National Shoe Fit program for stores and doctors/therapists so they can learn more about the anatomy of the feet and shoes and how to pair them up to create the best recipe for a person.
Now, onto this case.
In this case you should notice a few things.
1- the rigidity of the flat foot as portrayed in the photo where we are pushing up with our thumb on what once was the peak of the arch (yes, there are 5 photos in this case, click on one to enlarge or scroll) . We are attempting to push up, but the midfoot is completely rigid. This is a classic Rigid Flat Foot Deformity, A Rigid Pes Planus if you will.
2- There is a prominence at the navicular bone, both top (dorsal) and bottom (plantar) aspects of the foot (see photo of my hand with finger and thumb indicating these areas). The plantar prominence is the actual naviular bone (mostly) that has become weight bearing (termed “weight bearing navicular” and crudely by some as a dropped navicular, a term we dislike). And the dorsal prominence is a dorsal crown of osteophytes. This means a dorsal ridge of bone has formed at the navicular-1st cuneiform bone/joint interval because of the constant and repetitive compression of the two against each other dorsally as midfoot arch collapse occurred repeatedly and then became a fixed permanent entity.
3- The hyper dorsiflexion range at the 1st MTP joint (the big toe). This range is excessive at actually was able to exceed 90 degrees (see photo) ! Even at rest the hallux (big toe) is extended suggesting the volume of dorsiflexion it gets all the time. By the way, there was little to no hallux 1st MPJ joint plantarflexion (downward bend), not in a foot this flat. In fact most of that is from the contracture of the short extensors of the toes as noted by the photo showing the hammer toe formation (hammer toe = contractured short extensor myotendon, and to the long flexors as well). Hammer toes are almost always seen in a flat foot presentation, to a degree.
Now, lets put some things together (but a reminder, this is a single principle today, there are many more issues here).
Today’s Principle: Passing the Buck
Normally we need to have just slightly greater than 90 degrees of ankle mortise dorsiflexion to progress the body over the ankle. Put in other words, we need to be able to get the tibia slightly past vertical (perpendicular to the ground, hence 90+ degrees). Depending on the reference, anywhere from 15-25 degrees past that 90 degree vertical, thus 105 to 120 degrees) is the goal.
*So, a flat RIGID foot. If you jam an agressive orthotic (or possibly even a motion control shoe) under this foot it could very likely be painful to those rigid bony prominences and it will remove the client’s “passing the buck” compensation. Now the forces may have to revert to the proximal strategy at the knee. So, when do YOU go with the orthotic or motion control shoe ? When it comes to the feet, use your head. And, consider the Gait Guys, National Shoe Fit DVD program. Email us at : email@example.com