Also known as lowered arches, flat feet or excess pronation, hyperpronation describes a foot which pronates too much, for too long at the wrong time during the gait cycle.
Incidence in the general population: Very Common (67%)
This Pronator foot shape is caused by natural varus deformity that forces the Sub-Talar joint into a pronated position when the foot is fully weightbearing. As the foot goes through the Gait Cycle (the placing of one foot in front of the other in a rhythmic sequence), this pronated position of the Sub-Talar Joint disrupts the entire gait sequence.
Pronation equates to the mobile adapter state of the foot, where the joints are looser to enable the body to absorb shock. The foot should normally only act as a mobile adapter during the Foot Flat and Midstance phases of the Gait Cycle, when the full force of the body is acting vertically on the foot.
With a varus deformity, however, the foot remains pronated, and therefore acts like a mobile adapter for a much greater time throughout the Gait Cycle than is required.
As a result, during Foot Flat and Midstance when the weight of the entire body is over the centre of the foot, the foot is forced to “over-pronate”, causing excessive lowering of the medial longditudinal arch and inward rotation of the lower limbs.
The foot should re-supinate ready for Push-Off, but over-pronation means it is unable supinate sufficently. The result – a significant loss of energy and reduced power with which to propel the body forward. This instability during propulsion causes bunions to develop and fatigue and exhaustion in the legs, hips and back that worsens with prolonged standing/walking.
The degree of hyperpronation and the extent to which the arch lowers is related to the degree of natural varus in both the rearfoot and the forefoot.
Hyperpronation and poor posture
The effects do not stop there, however. Excessive pronation within the foot causes excessive internal rotation of the lower limbs which force the muscles in the legs to work in a different way.
This repeated motion with every single step eventually leads to the development of muscle imbalances and weaknesses throughout the lower extremities. In addition, the torsional stress within the knee and hip joint as a result of the prolonged internal rotation of the lower limbs throughout the gait cycle increases abnormal wear and tear of these weight-bearing joints.
Because movement, or patterns of movement in one part of the body must affect all other parts (a closed kinetic chain), the problems continue up through the body, affecting the back, shoulders, neck and even the head.