The E Quad foot-type is one of the most destructive foot-types of all.  The combined uncompensated rearfoot and forefoot varus deformities in this foot-type create a very rigid foot that is unable to provide the motions necessary to load the medial aspect of the foot during stance phase of gait.  It is for this reason that, when an individual with this foot-type is standing still, they will tend to stand on the outer borders of their feet with the inner side of the foot elevated from the ground.  These people hate to stand still because the only way to ever really load the inner side of the foot is to get the heel off the ground! Once in propulsion, the medial heel pivot will allow the medial column of the foot to eventually load.  But all this compensation gets tiring after a while, and causes repetitive torque about the midtarsal joint!  Even as a youth, and certainly by the time this person is in their teens, they are already showing signs of midtarsal joint breakdown and the acquisition of a reverse last foot shape.The key note feature of this foot-type is by far the ballistic heel whip that is evident at heel rise.  The larger the forefoot varus deformity the bigger the heel whip, the larger the toe sign, and the greater the chance of kicking themselves in the opposite leg. 

Contact Phase

At initial contact, the calcaneus strikes the ground in an excessively inverted alignment relative to the floor.  Since the rearfoot varus deformity is uncompensated, very little subtalar joint pronation is observed.  Normally, the forefoot should be lowered to the ground in a plantigrade position to conclude the contact period of gait.  Additionally, the foot should be in a semi-mobile state so that weight can easily transfer from the lateral to the medial side of the foot.  However, in the case of the Quad E foot-type, this does not happen!  At foot flat, instead of being plantigrade, the forefoot impacts the ground in a varus state of alignment.  Also, because of the rigid nature of this foot, it lacks the flexibility required to load the medial column.  As a result, excessive ground reaction forces are exerted onto the 5th metatarsal head and the medial aspect of the forefoot remains unloaded at the conclusion of the contact period.

Midstance Phase

As weight moves forward over the foot in midstance, the arch and midtarsal joint remain fairly rigid. The underlying rigid forefoot varus prohibits the normal pronatory twist of the forefoot from occurring, impeding proper loading of the 1st met head. If the forefoot varus deformity is not too large, it is possible that the peroneus longus may be able to plantarflex the 1st ray to achieve at least partial loading on the 1st MTH.  However, in the case of a larger forefoot varus deformity, the peroneals may fail to complete the job!  In such instances, the oblique midtarsal joint will begin to pathologically break down and you may begin to notice a bending, or lateral creasing, along the outer aspect of the foot.  You may also notice that the ankle appears to be bending inward toward the midline.  Acquired midtarsal joint laxity will ensue over time leading to progressive collapsing of the arch, impairment of posterior tibial functioning, and loss of integrity of the plantarfascial ligament.  But wait, there’s more!  Since the rearfoot remains uncompensated at the subtalar joint, the collapsing of the arch does not happen in a vertical direction (i.e. see midfoot sag referenced in foot types D and F), but rather in a medial or horizontal direction which we like to refer to as medial shelfing.Additionally, the medial shelfing coincides with abduction of the forefoot, or the development of what is called a positive toe-sign. This combination will cause the foot to acquire what we call a reverse last foot shape. Look at the left foot in this midstance picture and try to completely ignore the right foot. Looking at the outside edge of the left foot, you will notice a sharp angle as the forefoot bends out laterally. It almost looks like the arch is on the outsideof the foot.  If you cover the right foot over with your hand, you might easily mistake the left foot for a right foot!!

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Propulsion Phase

As the heel lifts off the ground, the 1st metatarsal head should be fully loaded. However, the emphasis here is on the word “should”, since in most E Quad foot-types the forefoot varus is too large and the medial column has not successfully loaded.  The most common compensation for this foot-type is a medial heel whip that occurs as the heel rises from the ground.  The heel whip maneuver requires a pivot point.  As the heel rises, the foot pivots around the 5th metatarsal head, transferring weight from the lateral to the medial side of the foot and finally loading the 1st metatarsal head. This medial heel whip creates heavy shearing and rotatory forces over the 5th metatarsal head, leading to a heavy circular callus formation. The medial heel whip also results in a narrow heel base gait. Runners with this foot-type often complain of “kicking themselves”. In the most extreme cases, even after the heel pivot, the medial side of the foot still may not be totally loaded.  When this occurs, the foot will have to rapidly “plop” down onto the medial column, driving the 1st metatarsal dorsally.  As a result, weight is transferred onto the 2nd metatarsal head causing callusing and potential for stress fractures. Final propulsion occurs off the medial edge of the hallux, resulting in a pinch callus.

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