Functional Leg Length Inequality (LLI) is very common among athletes. Simply put, it is when one leg is longer than the other due to any number of reasons. The one reason that isn’t included in this category is an Anatomical Leg Length Inequality. Anatomical Leg Length Inequality is when one leg is actually longer than the other due to structural problems. Functional Leg Length Inequality is caused by usually an Upslip or Anterior Rotation at the pelvis.
This occurs in approximately 60% of the general population. Clinically, you will see this in 90%+ of an athletic team. That will vary greatly depending upon the sport and level of activity of the team.
For example, collegiate basketball teams tend to have a very large number of Lumbopelvic Dysfunction and Functional Leg Length Inequality due to the repetitive nature of jumping and landing on and off of one foot. This will cause a great number of lumbopelvic issues because of of the dynamics constantly changing at the hip.
Sports such as swimming, track and even football will see a much lower rate of Functional Leg Length Inequality.
Functional Leg Length Inequality (LLI) has been extensively researched over the years because of it’s ripple effect up the lower extremity and spine. So, before we go any further, let’s look at what the research tells us:
- Approximately 60% of the general population has a Functional Leg Length Inequality
- 79% of people who experience lateral patella femoral pain have a Functional Leg Length Inequality
- Almost always occurs on the longer leg
- The body will increase the Q angle of a longer leg in an effort to shorten the leg. This increased Q angle will cause a lateral tracking of the patella and knee pain
- Links have been established between Funcational LLI and biomechanical abnormalities including increased lateral lumbar flexion, altered running mechanics, and shoulder leveling
So what does all of that tell us?
We must look at research, as it must be the basis of everything that we do. However, we also need to make sure that we pay attention to clinical outcomes and blend the two areas.
On first glance, many would say that leg length inequality is much to do about nothing. But, as you continue to dig deeper into the research, you see that the research performed with the athletic population, it becomes much more obvious that Functional LLI has an impact on the overall biomechanics of the body.
When you then add clinical experiences to the research, you see that if you aren’t looking at LLI when evaluating an athlete for a lower extremity injury, you are missing the boat.
Background and Etiology
There are 2 basic causes of an Functional Leg Length Discrepancy;
An athlete who presents with a Functional LLI should first undergo a basic Leg Length Evaluation. An athlete with a Functional LLI, will present with one leg shorter than the other, and an abnormal pelvic position. So, when landmarks of the pelvis are palpated, you will see that the Anterior Superior Iliac Spine (ASIS), Iliac Crest, and the Posterior Superior Iliac Spine (PSIS) don’t line up. This athlete will likely present with a history of low back pain.
The big take home from this is that when an athlete presents with a Functional LLI, it can be coming from a variety of sources. The Functional LLI is coming from somewhere, now the sign of a good clinician is being able to find it and then correct it.
Find the source of the problem and fix it!!
Other things which may be affecting an athlete’s lumbopelvic dysfunction include:
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