This study aimed at investigating the immediate effect of induced hyperpronation of the feet on the spine alignment in the standing position using an ultrasound-basis motion analysis system.
Three-dimensional motion analysis system, with ultrasonic pointer and basic system was applied for analysing the spine.
Initially, the barefoot participants were asked to stand in a relaxed position with their weight evenly distributed on both feet to obtain the same base of support considering their pelvic width and the same natural foot alignment.
Then, the participants stood on the posture wedge angled at 10, 15 and 20 degrees, which was designed to induce hyperpronation.
Tracing was then made of the participant’s feet so that all measurements were made with the participant in the same standing position.
The findings of the study suggest that during pronation of the subtalar joint, the calcaneus everts, causing the talus to slide medially and inferiorly.
This medial downward movement of the talus induces an internal rotation of the tibia and this may affect the knee joint function.
Medial rotation of the femur causes the head of the femur to exert pressure on the posterior portion of the acetabulum.
It has been hypothesized that internal rotation at the femur causes the head of the femur to exert pressure on the posterior portion of the acetabulum.
This backward push on the posterior aspect of the pelvis would cause the pelvis to tilt anteriorly.
Because the pelvis is tightly connected to the lumbar spine at the sacro-iliac joint by an extensive fibrous connection, an anterior tilt of the pelvis could increase the lumbar lordosis.
An excessive anterior tilt of the pelvis may lead to an increase in the lumbar anterior convexity.
The posterior convexity of the thoracic curve increases and becomes kyphotic to balance the lordotic lumbar curve and maintain the head over the sacrum.
The results of this study revealed that sacral angle, pelvic inclination, lumbar lordosis and thoracic kyphosis increased with an increase in bilateral foot pronation.
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