Limb Length Discrepancy and Back Pain

“My chiropractor said one my legs is longer than the other and that is why my back hurts?  Is he right?”

It seems that 100% of my patients that have seen chiropractors in the context of back pain come in and inform me that they have been told they have one leg longer than the other.  And that is why their back hurts, right?

I read a study recently that shines a light leg length analysis.  The study by Schneider et al. looked at “Interexaminer reliability of the prone leg length analysis procedure.”  (J Manipulative Physiol Ther. 2007 Sep;30(7):514-21.)  In this study, two chiropractors examined a series of 45 patients with a history of low back pain.  The results of the study were interesting.  Two notable findings included:

1.  There was no significant correlation found between the side of reported pain by the patient and the side of the short leg as noted by either clinician
2. All of the patients (100%) were judged to have a leg length difference by both clinicians

A related study demonstrates a frequent discrepancy between clinical leg length measurements and difference measured with standing x-rays. (J Manipulative Physiol Ther. 1995 Jul-Aug;18(6):343-6.)   The authors of this study conclude that “prone leg length measurements for inequality are not entirely valid estimates of standing X-ray differences. Large differences between prone and X-ray measurements in some cases indicate that one should be cautious when using the prone method alone to estimate leg length discrepancy.” (J Manipulative Physiol Ther. 1995 Jul-Aug;18(6):343-6.)

So, what does all of this mean?  It is hard to say.

There remains a fair amount of debate about what to make of leg length discrepancies.  There are some studies that do show some improvement in back pain with use of lifts in the context of small leg length discrepancies (Arch Phys Med Rehabil. 2005 Nov;86(11):2075-80.) 

More often than not, though, observations by a clinician of discrepancy in apparent limb length are likely “functional” rather than “structural.”  That is, a person with back pain often has some muscle spasm, maybe some slight rotation in the pelvis and all of these factors can lead to some perception of side-to-side differences in leg length.  Do 100% of patients with back pain have this kind of asymmetry?  I have a hard time imagining that is true. 

So, if someone tells you that your legs are different lengths try a lift if you want.  It’s an inexpensive, reversible intervention that might be helpful.  But I would not lose too much sleep or think that you are freakish and have asymmetric limbs growing out of your body. 

Some people come in to see me after being told of their apparent discrepancy and act as though this revelation explains everything about why they have pain.  Maybe it does play a role.  But remember that you are not the first (or the last) person to be given this information.  And remember that there is no clear evidence that these observed differences are causal or even correlate with the side of pain.