The structural leg-length inequality caused by the shortening of a segment of an extremity, results in an altered position of lower limb joints, the pelvis and the spine in static as well as dynamic conditions. That may induce a disturbance of the postural control.

The objective of this study is to investigate the effect of the structural LLD on the control of the posture.

The measurement of the weight distribution and the static posturography is performed on the balance platform Good Balance by Metitur . The device is comprised of the triangular force platform (800 mm x 800 mm x 800 mm) with electronic system and computer software. The body weight distribution is evaluated in the upright standing with eyes open, feet placed 20 cm from each other or narrower in children, with upper extremities in relaxed position by sides. The individual stands motionlessly for 15 s, then the measurement is recorded. The results of each lower extremity loading and a difference in weight bearing between extremities are expressed in percentages (%) .

The static posturography examination is performed with 3 various positions of feet, both with eyes open (EO) and eyes closed (EC). (1) Position : normal standing - an upright standing with feet placed parallel 20 cm apart. (2) Position: tandem - a stance with one foot placed ahead of the other, medial edge of feet was put on the midline of the balance platform. In the experimental group 2 trials were recorded: (a) foot of the shorter leg in the front, (b) foot of the shorter leg in the rear. In the control group also 2 trials are performed: (c) foot of the right leg in the front, (d) foot of the left leg in the front. (3) Position: one leg standing: stance on the one leg, foot placed 10 cm from midline of the platform, the other - 90 degrees flexion of the knee and the hip, test performed only with EO. Every participant is supposed to stand motionlessly for 30 s in normal standing , or for 20 s in tandem .and one leg standing position. Conditions of the posturographic examination involved : quiet and normally lit room , standing barefoot , the eyesight directed at a point in the distance of 2 m , glasses or contact lenses are worn if they are normally needed, arms held in the front of the body with hands together in order to limit movements of upper extremities . The recording is initiated when a stable position is attained . Each test is performed once .

Mean velocity (mm/s) of COP sway is measured as a quantitative parameter of the postural control assessment . Mean COP sway velocity is recorded both in anteroposterior (AP) and mediolateral (ML) directions .

Inclusion Criteria:

• for patients: structural leg length discrepancy
• for healthy volunteers: symmetrical length of lower limbs

Exclusion Criteria:

• for patients: achondroplasia, non-union, idiopathic scoliosis, extremity shortening in the course of neurological disease (e.g. Cerebral Palsy), vestibular disorder (e.g. Ménière's disease), diabetes, sensory disorder, intake of medications affecting psychomotor activity, dizziness, neurological diseases (e.g. epilepsy), BMI>30, using mobility aids (e.g. crutches)
• for healthy volunteers: leg-length discrepancy, scoliosis, faulty posture, vestibular disorders, diabetes, intake of medications affecting psychomotor activity, dizziness, sensory disorders, neurological disease, BMI>30.