Leg length discrepancy (LLD) is oftentimes blamed for foot, ankle, knee, hip and back pain. When we are in pain, it is normal to look at a quick fix in giving a heel lift or orthotic to “fix” this issue. Currently, there is controversy around how much, if any, may even cause pain or dysfunction. Some clinicians may say that participating in repetitive sports such as running may cause a stress fracture or back pain compared to those without. Research varies in identifying the finite difference between left and right that causes dysfunction and pain, ranging from 0.3 cm to 1.0 cm and greater. (1,2)
- In the U.S. Military Academy (USMA), approximately 10% of cadets experience a lower extremity injury in their first year. You will often times see research coming out of the USMA or any division of it for two reasons: 1. Our safety depends on their health 2. There is a massive sample size of data to look at. Research by Gross et al studied 1,100 cadets in 2005 and screened them for leg length discrepancies. After screening, 11.5% were deemed to have LLDs >0.5cm and ranged from 0.5 to 3 cm. Over the course of one year, the cadets with the LLDs and the control group were compared. In this time, 25 of 126 cadets with LLDs were injured a total of 30 times. In the control group, 22 cadets were injured a total of 28 times. This effectively demonstrates that leg length had no influence on their lower extremity injuries.
So what does this mean? If you have a leg length issue, it should still be screened and should not be ignored. Some ways we screen this is through looking at iliac crest (pelvis) height, measuring from greater trochanter (bony spot on your hip) to lateral malleolus (ankle bone), ASIS to medial malleolus and today’s gold standard of an x-ray. You can and should also measure leg length loaded (standing) or unloaded (lying down) as well. Understanding the type of LLD is also important. There are 3 primary types:
- Anatomical: distance between the greater trochanter and lateral malleolus
- Functional: limb shortening/lengthening caused by joint contractures, muscle asymmetry or axial alignment
- Clinical: combination of anatomical and functional LLD
Learning the type of LLD may be informative regarding what is and is not modifiable. Changing an anatomical leg length issue is rarely advised as you would require an osteotomy which is a surgical correction. However, if someone is determined to have a functional leg length discrepancy with asymmetry in their pelvis and surrounding muscle, it can and should be changed. The research noted above also demonstrates the fact that a heel lift may be an unnecessary addition to your shoe given the fact that there were no orthotics/heel lifts and no measurable difference in injury rates (1). That being said, as stated earlier, there is a large range of inconsistency on what should and should not be corrected or lifted. Before putting a lift in your shoe or correcting it, consider this: Most importantly, leg length is a test in itself. It does not tell the whole picture. What will give us a greater answer as to why someone may be in pain, whether soccer, running, cycling etc, is assessing each person in dynamic positions–assessing joint mobility, tissue extensibility, strength and stability. Dynamic movement screens such as the Functional Movement Screen (FMS) or Selective Functional Movement Assessment (SFMA) will give us the roadmap of where to go, what movement is done well and what can be improved. References
- Gross, Donald L., MAJ, Josef H. Moore, SP, USA, Erin M. Slovak, SP, USA, and Brian S. Hatler, MAJ. “Comparison of Injury Rates between Cadets with Limb Length Inequalities and Matched Control Subjects over 1 Year of Military Training and Athletic Participation.” Military Medicine 171 (2006): 522-25. Web.
- Brady, Rebecca J., John B. Dean, T. Marc Skinner, and Michael T. Gross. “Limb Length Inequality: Clinical Implications for Assessment and Intervention.” Journal of Orthopaedic & Sports Physical Therapy 33.5 (2003): 221-34. Web.