Anatomical Leg Length Inequality is more common than you think, and plays a large role in the function of the entire body. It can be defined as “A structural difference in limb length in either the left or right legs.” Meaning that there is an actual difference in length of the bones or structure of a leg. This is different than Functional Leg Length Inequality, where the bones are equal length, but there is a rotation or upslip which is causing the legs to appear unequal.
Anatomical 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:
- 90% of the general population have an Anatomical LLI with a mean average of 5mm (about 3/16 in.)
- 1 in 1000 people have an Anatomical LLI greater than 20mm (3/4 in.)
- Statistically, only those who present with a LLI of greater than 20mm (3/4 in.) are correlated to low back pain
- The right leg is shorter 53-75% of the time depending upon which research you look at
- There is a strong presence of low back pain and/or lower extremity injury for military personnel with Anatomical LLI of 5mm or greater
- This research theorized that those who repetitively and continually load are more sensitive to LLI (would also apply to athletes)
- One study demonstrated that athletes with patellar tendonitis had a greater LLI than those athletes who were asymptomatic (5.8mm vs. 3.0mm)
- Individuals who have genetic Anatomical LLI are much less likely to be symptomatic than those who develop their LLI suddenly
- Bones of the hip, sacrum and lumbar spine will change shape and change the angles of the joints to accommodate the LLI
- Those who develop a LLI later in life will be much less likely to tolerate LLI because their skeleton is rigid and less likely to adjust to a descrepency
So what does all of that tell us?
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 military personnel and the athletic population, it becomes much more obvious that Anatomical 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 Anatomical Leg Length Descrepency;
Congenital Anatomical LLI occurs because an athlete genetically grows one leg longer than the other. This is very common, as discussed above, and occurs for no known reason. Typically, these athletes don’t have as many issues or injuries as athletes with a sudden onset.
Individuals with a sudden onset of an Anatomical LLI have a LLI due a fracture that doesn’t heel normally or they have a joint replacement. These things typically happen when the skeleton is at least partially mature, making the body much less likely to tolerate such an injury long term.
An athlete who presents with an Anatomical LLI should first undergo a basic Leg Length Evaluation. An athlete with an Anatomical LLI, will present with one leg shorter than the other, and a completely neutral pelvis. 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) are all even. This athlete will likely present with one knee unequal to the other when they are lying supine on a table with their knees bent at 90 degrees and their feet even.
An athlete with an Anatomical LLI may also present with an Anterior Rotation or an Upslip with an equal leg length. Once the Anterior Rotation or Upslip is fixed, the athlete’s Anatomical LLI will become much more apparent. This is why athletes must not only be evaluated for a LLI, but also for Lumbopelvic dysfunction as part of a full biomechanical evaluation.
There are a number of techniques that have been used in an effort to correct an Anatomical LLI. Most of them involve some sort of a procedure to either shorten or lengthen a limb with an aggressive surgical procedure. Unfortunately, there are very mixed outcomes with virtually all of the procedures. And, most surgeons will only attempt such a radical procedure on very large cases of LLI.
The heel lift is the treatment of choice for an Anatomical LLI. This is of course assuming that a Functional LLI and any kind of lumbopelvic dysfunction has either been ruled out or corrected. Using a heel lift on such athletes will likely only make the symptoms worse.
The heel lift is inexpensive and simple. Athletes typically see very quick results and tolerate the lift well.
Be careful, however, not to make it too large as it can have a tendency to make an athlete’s heel slip out of their shoe. If they need a lift that large, do your best to balance between making up the difference in leg length and keeping their foot in their shoe. Many times this can be combated with different lacing techniques as well.
Because of the long term accommodations that the bones and joints can make for an athlete who has a congenital Anatomical LLI, we also need to keep in mind that a lift may not be for them. Or, you may have to try a small lift first, and gradually move to a lift which is more in-line with their discrepancy.
Other things which may be affecting an athlete’s lumbopelvic dysfunction include:
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