X-ray of leg length in children

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Author: Mikael Häggström [notes 1]



Suspected leg length discrepancy.


X-ray scanogram or 3-joint standing X-ray with ruler.[1] Full limb X-ray should not be used because of projectional distortion.


X-rays for leg length measurement.

Using the ruler in the images (either directly or for calibration of measuring software), measure the femur and the tibia both separately and combined. Various measuring points for these purposes have been described,[notes 2] but a functional method is to measure the distances between joint surfaces:[2]

  • Femur length: The superior aspect of the femoral head to the distal portion of the medial femoral condyle.
  • Tibial length: The medial tibial plateau to the tibial plafond.
  • Combined: The superior aspect of the femoral head to the tibial plafond.[notes 3]

Also take at least a quick look at all the projected skeleton for any other apparent deformities.


  • Femoral and tibial length on both sides, their difference, as well as the points used for the measurements.[notes 2]
  • Total length of these, and their difference.


The femur measures 424.6 mm on the right side and 421.5 mm on the left (3 mm shorter), measured down to the medial condyle.

The tibia measures 340.0 mm on the right side and 322.9 mm on the left (17.1 mm shorter), measured between the medial plateau and the plafond.

Combined, these measure 768.9 mm on right side and 747.6 mm on left (21.3 mm shorter).[notes 3]

This example is Public Domain, and can be copied without any need for author attribution.
See also: General notes on reporting


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.
  2. 2.0 2.1 Apart from the points mentioned in this article, articles have suggested for example a line between the femoral condyles for both the femur and the tibia as a surrogate for both the distal end of the femur and the proximal end of the tibia:
    - Werlang, Henrique Zambenedetti; Oliveira, Gabriel Antônio de; Tamelini, Ana Maria; Madalosso, Ben Hur; Maciel Júnior, Francisco da Silva (2007). "Escanometria dos membros inferiores: revisitando Dr. Juan Farill ". Radiologia Brasileira 40 (2): 137–141. doi:10.1590/S0100-39842007000200014. ISSN 0100-3984. 
    Another definition of femoral length is between the center of the femoral head and the center of the femoral notch, and the tibia length as between the center of the tibial plateau and the center of the tibial plafond.
    - Guenoun, B.; Zadegan, F.; Aim, F.; Hannouche, D.; Nizard, R. (2012). "Reliability of a new method for lower-extremity measurements based on stereoradiographic three-dimensional reconstruction ". Orthopaedics & Traumatology: Surgery & Research 98 (5): 506–513. doi:10.1016/j.otsr.2012.03.014. ISSN 18770568. 
  3. 3.0 3.1 Alternatively, it could be calculated as the sum of the femur length and the tibial length, but this omits the knee joint distance. Nevertheless, the measuring method does not need to be mentioned in the report, because in the rare occurrence that anyone needs to know what method was used, they can mathematically conclude whether the combined length is the sum of the femur and the tibia, or whether it is slightly longer because of the included knee joint.


  1. . Leg Length Discrepancy (Pediatric). Columbia University. Retrieved on 2019-02-14.
  2. Sabharwal, Sanjeev; Kumar, Ajay (2008). "Methods for Assessing Leg Length Discrepancy ". Clinical Orthopaedics and Related Research 466 (12): 2910–2922. doi:10.1007/s11999-008-0524-9. ISSN 0009-921X.