Repeatability and reproducibility of measurements in various diagnostic methods is still the main problem in the diagnosis of the anatomical and biomechanical limb distortion. Goal of the paper. Aim of this study was to evaluate the reproducibility and accuracy of measurements of selected lower limb biomechanical parameters obtained using navigated ultrasound and rentgenometry. Material. Research group was composed of 55 subjects, both with and without clinically observed distortion of the lower limbs, at the age of 10-77 years (mean age 35.75 years). Method. The results of the measurements obtained with the software of navigated USG - Bonefix were compared with the results of measurements of the same parameters obtained with X-ray measurements of the lower limbs. The following parameters were calculated in each test, in both legs: distance between the hip and ankle (mechanical axis of lower limb – Mikulicz’s line) distance between the hip and knee, femoral-tibial angle, distal lateral femoral angle (LDFA) proximal tibial angle lateral (LPTA). Data obtained from measurements, of each feature of the lower limbs, with ultrasound and rentgenometry were analyzed with ICC coefficients and Pearson correlation coefficients (r) between the results of both methods. Results. Statistical analysis of the results indicated a very high compliance for the measurements performed with navigated ultrasound and rentgenometry for all the parameters (ICC = 0,862-0,975) except for the measurement of femoral-tibial angle (ICC = 0275 - 0.563). Conclusions. The results of the research indicated that the assessment of biomechanical parameters of the lower limbs with navigated ultrasound is as accurate and shows a strong similarity to the results of the same parameters obtained from the rentgenometry.