Introduction. Foot arch condition plays an important role in correct setting of lower limbs joints, proper muscles tone and well-being . More and more frequently foot arch deviations affect population of school age children [2, 3]. It is based on anatomic knowledge that abnormal foot arch is strongly connected with the disturbed muscle tone of lower limb. The aim of the presented study is to evaluate the relation between the foot arch condition and muscular balance of the lower limbs.Material and methods. Children were assessed using the Clarke’s angle and indicatory muscles length tests including: quadratus lumborum muscle, hamstring muscle, thigh adductors, piriformis muscle.Results. Abnormal foot arch was showed by 70% of subject children. The greatest number of muscles length abnormality was observed in quadratus lumborum muscles. There was a statistically significant correlation between right hamstring muscle contraction and abnormal foot arch (p = 0.011). Conclusions. Foot arch alternations increasingly more often appear in the greater number of school–age children. The assessment and therapy of abnormal foot arch should include the examination of muscular balance of the lower limbs.