Hyperpronation is a condition afflicting the foot and ankle. It is characterized by excessive inward rolling of the foot at the ankle and consequent flattening of the arch during gait movements. Though this condition is sometimes described as a fallen arch, or flat feet, hyperpronation is in fact not a dysfunction of the tissues of the arch of the foot but rather a joint problem, in which multiple bones of the foot simultaneously rotate in the wrong direction relative to one another. In addition, the muscles of the calf and foot may become imbalanced in an attempt to compensate for the adjustment in gait caused by this condition, which may set off a chain reaction that disrupts the function of other muscles involved in locomotion.
One or more preexisting muscle imbalances caused by daily movements over time can cause hyperpronation to develop. A possible cause is weak hip abductors, namely the gluteal muscles in the back of the hip, as a consequence of obesity and/or sitting for long periods. Another is an Achilles tendon that is too short, generally from wearing high-heeled shoes. Hyperpronation may also be caused by wearing shoes that are too tight and that therefore disable the muscles on the underside of the foot that flex the toes. Finally, it may be caused by a dysfunction of the tibialis posterior tendon, a tendon of a deep muscle in the calf that runs under the foot and is supposed to bend the foot downward at the ankle as well as supinate the foot, or turn the sole inward.
Visible as the flattening of the inside of the foot toward the ground, hyperpronation is actually a series of motions occurring simultaneously in several foot joints during gait movement. One such motion is calcaneal eversion, in which the calcaneus or heel bone strikes the ground at a slightly inward-tilted angle, so that the underside of the heel tilts outward. Another involves the head or front surface of the talus bone, that above the heel bone and just below the ankle joint, tilting too far inward and in a downward direction. This causes the joint between the talus and the navicular bone, a small foot bone in front of the talus, to supinate, which means the midfoot rotates laterally or outward and superiorly or upward.
Ahead of the arch of the foot, hyperpronation involves the abduction or outward angling of the forefoot with simultaneous dorsiflexion as the body’s weight transfers onto the ball of the foot. This means that as the joint beneath the big toe makes contact with the ground, that toe angles toward the other toes and at the same time elevates away from the ground. Over time, this repeated motion increases the risk of hallux valgus deformity, better known as a bunion. In addition to causing foot problems like bunions and plantar fasciitis, hyperpronation can lead to a chain of muscle imbalances that can cause everything from knee pain to poor posture.
To treat hyperpronation, it is recommended that sufferers avoid tight-fitting shoes and minimize the wearing of high-heeled shoes; in fact, they are encouraged to walk barefooted to strengthen the foot and ankle muscles and stretch the Achilles. Stretches for the calf muscles and Achilles tendon are recommended, as are strengthening exercises for the deep toe flexor and tibialis posterior muscles. These may include picking up objects with one’s bare feet, walking on one’s toes in bare feet, and performing calf raises with an inverted foot, in which one lifts the heels off the floor while simultaneously allowing the ankles to roll outward.