The torsional malalignment of lower limbs in children can be measured by different diagnostic techniques. In this review, clinical examination, radiographic technique, ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) are explained; advantages and disadvantages are described; and recommendations are given for their appropriate application. Clinical determination of femoral and tibial torsion can be applied easily to patients and does not require special equipment. The method is regarded not to be reliable enough for preoperative planning and does not allow a reproducible documentation of results. With standard radiographs, torsional deformities also cannot be measured reliably enough. A further disadvantage is the radiation exposure to the patient. Ultrasonography, as a radiation-free technique, has shown to produce valid and reliable results in measuring torsion of the lower limbs, but the documentation of results for preoperative considerations is hardly possible. With CT and MRI, sector-scanning techniques are available for precise and reproducible assessment of post-traumatic torsional deformities in the femur and tibia of children. Although CT scanning still poses a radiation hazard to the patient, MRI is free of radiation and allows a precise anatomic measurement even in nonossified structures. The comparison of different techniques in a recent investigation has shown a high correlation of results between MRI and CT scanning and between MRI and ultrasonography. Reliability of techniques was high in MRI and CT, but less in ultrasonography and clinical examination. Clinical examination and ultrasound techniques are recommended for screening purposes in post-traumatic torsional deformities in the lower extremities in children. For operative considerations, the sectorscanning techniques CT and MRI should be used, with priority given to MRI in children.