A scanogram is a technique similar to regular plain x-ray in which an image of the whole lower limb is taken on a single film. It shows the lower limb starting from the pelvis and down to the ankle joint.
The image is then processed using a computer to determine certain accurate measurements. The length of both lower limbs are measured to determine any inequality. This is especially important before lengthening procedures.
Scanograms are also very useful for measuring deformities of the lower limbs e.g. knock-knees and bow legs. In such cases a line is drawn from the center of the hip joint to the center of the ankle joint. This line should pass near the center of the knee joint. If there is deformity of the lower limb this line will pass medial or lateral to this point.