The “Flatfoot” – Abnormal or Excessive “Pronation”

THE EVALUATION PROCESS for PRONATED FEET

Often the practitioner observes a “pronated” foot, assumes it is in need of ‘correcting’ so proceed to assess and evaluate the “abnormal pronation” in off weight bearing, passive range of motion testing. The child may even be ask to stand in place while we ‘measure’ the angular relationship of the posterior heel to posterior leg or supporting surface. The amount or degree of soft tissue, generally an abundance of fat tissue, is measured relative to the ground and we BELIEVE (often incorrectly) this to be a valid measure of calcaneal position; all with another assumption that the calcaneous is not being influenced along the parasagittal or frontal planes of the lower extremity and/or supra-pelvically.

Decisions are made based on this static presumptively abnormal posture that is easily perceived as a localized “problem” and then assume that we can Fix this during walking or running as translatory moments, vectors and centers of gravity are rapidly changing from our original static, standing position.

Go ahead, try to “hold” the calcaneous vertical as twice or three times body weight while 3-dimentional motion occurs above the continuously moving lower limb moves along a parasagittal plane of stance phase.

 

Subtalar Joint (STJ) or “Lower Ankle Joint”:

The most discussed and implicated joint in pes valgus, flat or pronated feet and high or cavus feet.

The STJ has been implicated in almost all flatfoot types and is blamed as the culprit as soon as an excessively pronated or everted foot is observed. However, in many cases, particularly when neuromuscular conditions exists, we are focusing inappropriately on this joint.

There are all sorts of descriptions of how the subtalar joint “actively “moves. It is actually 3 joints, or joint surfaces, that are generally combined as one joint functionally. The joint does not actively “move” but rather is driven, and converts motion within anatomical and environmental constraints. The big tension setter is the Achilles tendon which delivers the tension from the calf muscles, the knee, and hip muscles combined. The Achilles attaches to the heel at the very back surface. That becomes a fixed point.  That point is the point of a cone lying on its side. The foot or better yet, ‘leg’ moves in a near conic track around that tethered point as the joint surfaces of talus, calcaneus, navicular and the rest adapt  to ground forces and hip-knee-ankle coupling and musculotendinous linkages.

Anatomically, the subtalar joint is described as being comprised of two bones. The talus and the underlying heel bone or calcaneous. This however, does not provide any insight regarding the management of a child’s excessively pronated foot.

Other than along a parasagittal plane where the talus has almost all of its motion (dorsiflexion/plantarflexion), it may be observed to move medially/laterally but not alone. It is so snugly confined and locked in the ankle mortise (between medial malleolus of the tibia and lateral malleolus of the fibula) that it must be considered as a true extension of the leg. So functionally, the most basic description of the STJ is the tibia-talus-calcaneal coupling ; nothing less will do.

To describe STJ compensatory motion, the hip-knee coupling must also be included. All it would take would be a mild to moderate degree of hamstring reactivity, tension or contracture to affect the swing or off weight knee extension to effectively ‘remove’ the STJ out of the functional role at the moment of initial foot contact during stepping or walking. Yet, many professional continue to focus on STJ alignment and control when it is not a functional, weight bearing element at which compensation might pose a problem.

However the location of undesired or excessive pronation must be determined and at what point in the gait cycle does it need to be modified if efficiency and conservation of energy during gait are to be attained? Don’t assume that the heel eversion or valgus position arises at the subtalar joint (STJ). Most often, with neuromotor disorders the STJ is least problematic although at first glance it appears to be the source of permissiveness and compensation. Sure, if the heel is everted it MIGHT be at the STJ or then again with modest tension of the hamstrings or gastrocnemius alone, the midtarsal joint would permit the clinical eversion and not the unweighted calcaneous.

Basic understanding of planal dominance of the Ankle, STJ and MTJ would be of significant assistance along with a simple understanding of how the hip-knee-ankle-foot coupling system enhances or inhibits a child’s gait or posture.

the problem is limitation of Tibial / leg rotation forward, over the foot

 

So to reestablish the long medial / inner arch, just pushing up on the arch and/or pushing the talus to either restrain or correct, fails miserably.  UNLESS !!! THERE IS LIMITED OR NO WEIGHT ACCEPTANCE OF THE CALCANEOUS; such as in an “Equinus”(plantarflexed position of the calcaneous). An equinus position relative to the weight bearing surface may result from a limiting/tight Achilles muscle group, hamstrings, hip flexors or a contribution from each segment.

We need to asking “why” the off-weight bearing foot morphed into a ‘rolled-in’, apparently collapsed, ‘flat or fat’ appearing blob when it accepted partial or full weight?
What we know about intrinsic structural foot shape integrity is against rationale thought, logic and particularly our clinical observations. Surgically removing soft tissue elements from the medial or long arch side of a foot does not cause an apparent or real collapse of the foot. The collapse occurs when you remove or elongate the ligaments from around the calcaneal cuboid area especially near where an extension of the tibialis posterior tendon happens to also be located. As demonstrated surgically and published in the literature, the short and long lateral-plantar ligaments are key structures in the alteration of the medial long arch and its shape during weight bearing.
Often thought to be a mild, normal variation is the modestly flat appearing feet that can be much more painful than some very severe looking flat feet. These may be ordinary, average appearing feet when not being step upon but are submitting to being twisted and torqued  by tight or short muscles of the Achilles group most commonly. Not infrequently combined with tight hamstrings at the same time. The observed compensation within the feet serve to accommodate the limited length or excursion of the calf muscles, hamstrings or even the hip flexors. So, do not try to lift, elevate or even think about changing the excessively valgus, pronated, flat-appearing long arch IF the posterior muscles are short or limited in motion (Equinus is one of the most deforming forces of the weight bearing foot.). The equinus must either be corrected or accommodated if the feet are to retain any semblance of ‘normalcy.’