Investigation of the Effects of Different Subtalar Joint Pronation Amounts on Lower Extremity Anatomical Measurements, Jump Performances and Postural Stability in Healthy Individuals

The foot has an important role as it supports body weight and plays a vital role during movement. The ankle complex consists of the talocrural and subtalar joints, which have diagonal axes that perform multi-planar movements. Because of its oblique axis, the subtalar joint can produce three-planar movements, pronation, and supination. Foot pronation consists of medial rotation and adduction of the talus, eversion of the calcaneus, and abduction and supination of the forefoot. Medial longitudinal arch height decreased or disappeared in feet in pronation posture. Loss of medial longitudinal arch height requires that the foot cannot absorb enough energy and must produce more force to stabilize it. In particular, abnormal alignment in the hyper pronation posture or prolonged pronation is defined as both a risk factor and an etiologic factor for increased navicular drop and malalignment patterns in the lower extremities. It is a possible etiologic cause for the development of most lower extremity overuse injuries by altering kinematics and force distribution. The lower extremity consists of segments that can be affected by the relative position of each other. Deviation of one segment from its normal alignment in the lower extremity also affects the alignment of other segments. In the frontal plane alignment, the hip joint can be affected from proximal to distal, while the foot and ankle complex can be affected from distal to proximal. Increased subtalar joint pronation in the kinetic chain from distal to proximal is associated with decreased dorsiflexion angle and increased frontal plane projection angle. It has been shown that ankle dorsiflexion limitation causes changes in the biomechanics and kinematics of landing after jumping, but no study examining the effect of foot pronation on jump tests has been found in the literature.

Since the foot is located at the most distal point and acts as a support base for the kinematic chain, the smallest dynamic change in the foot affects the balance of the whole body. Due to foot pronation, changes in the sole contact surface may make it difficult for the foot to adapt to the ground, balance and postural stabilization may be adversely affected, and an increase in the workload of the muscles around the joint may be observed. It is mentioned that there is limited evidence about the effect of foot posture on postural stability. there is a need for studies examining the effects of different subtalar joint pronation amounts on lower extremity alignment, jumping performance, and postural stability. Our study will contribute to the literature with this aspect.