The Quad A Foot-Type is commonly thought of as an over-supinated or severe Pes Cavus foot. This condition, also known as a Torque Foot, occurs when a Uncompensated Rearfoot Varus is coupled with a Large Rigid Forefoot Valgus.
Point of Propulsio
OBSERVATIONS
High Arches
Rigid Feet
Lateral Pressure
Ankle Instability
Poor Shock
Attenuation
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for Quad A Foot Type
Quad A Orthotic
QUAD A FOOT TYPE
We fondly refer to this foot-type as our "chandelier shakers"!
Why? Because this foot-type loads heavily on the ground and never seems
to pronate, leading to poor shock attenuation.
The development of heel and lower back pain is common. The torque
foot nature of this foot-type allows the valgus forefoot to offset the
uncompensated inverted heel alignment that would normally lead to a toe
out gait pattern (see C Quad foot-type). Overall, the foot
progression angle for this person is such that the feet point
relatively straight ahead during gait (no toe out) with a narrow base
of support, much like a tight rope walker.
Contact Phase
At initial contact, the calcaneus of the Quad A foot-type strikes the ground in an excessively inverted or supinated alignment relative to the floor. Since the rearfoot varus deformity is uncompensated, very little subtalar joint pronation is observed as the forefoot is lowered to the ground to conclude the contact period of gait. The valgus alignment of the forefoot subjects the 1st metatarsal head to excessive and premature forces. In turn, the peroneals contract early in order to offset excessive supination of the subtalar joint. Also, because of the lack of subtalar joint pronation, there is significant loading force on the lateral side of the heel causing poor shock attenuation.
As weight moves forward over the foot, the arch and midtarsal joint remain rigid, with excessive pressure borne along the lateral column and base of the 5th metatarsal. Normally by this point in the gait cycle, weight begins to transfer from the lateral side of the foot over to the medial side. Instead, in the over-supinated Quad A foot-type, this weight transfer does not occur
IIn propulsion, the gastrocsoleus contracts, plantarflexing the ankle and initiating heel rise. The gastocsoleus also functions as an ankle invertor, since it’s insertion lies medial to the subtalar joint axis. As the rearfoot is already overly supinated in this foot-type, any additional supination caused by the contraction of the gastrocsoleus can lead to lateral ankle instability and the potential for sprains. As the subtalar joint moves into more and more supination, significant pressure is exerted on the head of the 5th metatarsal.
In terminal propulsion, the neuromuscular mechanisms of the body act to prevent spraining of the ankle. The foot and ankle must either rapidly pronate to shift weight back over to the 1st metatarsal; or, in many cases, a person with this Quad A foot-type will simply end their step early (short steppers).
Rapidly pronating the foot from the lateral to medial side in terminal propulsion creates pressure and instability across all the metatarsal heads. This results in heavy callus formations (particular the 1st and 5th metatarsal heads), hallux abductovalgus deformity, and hammertoes. Imagine grinding a rolling pin back and forth over the ball of the foot every step you take! This rapid and repeated transfer of weight from the medial to lateral, and back to the medial side of the foot is referred to as the “supinatory rock”