Used to assess for leg length discrepancy ​

With the patient supine, the patient brings the knees so that they are equally flexed to 90 degrees with the hips at roughly 45 degrees of flexion​

If the heights vary, there may be a leg length discrepancy ​

One leg more anterior on lateral view, indicates longer femur

On leg taller from anterior view, indicates longer tibia ​

Assess for anatomical leg length discrepancies, not functional discrepancies.