I often hear patients tell me that they are having pain in their hip or low back because they have
one leg longer than the other one. In fact, I find that people are often proud of the fact that they have one leg longer than the other. Well, I hate to break it to everyone but nearly everyone has one leg that is longer than the other one. In fact, according to this study http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1232860/, 90% of people have a leg length discrepancy with the average being 5.2mm.
So biomechanically does it make a difference if one leg is longer than the other? In this uniquely designed study http://www.ncbi.nlm.nih.gov/pubmed/22744469, they simulated leg length differences in subjects to see what the effects would be biomechanically while they walked in regards to the pelvis and lumbar spine. What they found was that the leg length differences had very minimal changes to the biomechanics. In another study http://www.ncbi.nlm.nih.gov/pubmed/18510741, they found that leg length differences had no effect on lateral hip pain. In yet another study http://www.ncbi.nlm.nih.gov/pubmed/9413588, they found that 1-2cm leg length differences had no effect on lower extremity joint biomechanics. So is your 1cm leg length difference that never seems to completely go away really the cause of your pain?
Can a leg length difference cause issues in the body? Absolutely! I’m not saying that it can’t. What I am saying is that I think a lot of therapists are too quick to point to the leg length difference as the culprit for the patient’s pain when it is a pretty normal finding. I feel that a lot of therapists will make patients continue to come back for treatment for a longer period than what is necessary because of this leg length difference that they continue to easily find. It is easy to have a hammer on your toolbelt and to use that hammer on every patient regardless of if it is the correct tool for that patient. What if the patient’s 1cm leg length difference is how their body is made?
In conclusion, the human body is asymmetrical by nature and leg length differences are very common. The next time someone tells you your hip pain is being caused by one leg being shorter than the other leg, perhaps you should dive deeper into the matter. The literature shows that the body can adapt to these normal discrepancies but a significant leg length difference, generally greater than 1cm, could potentially be the source of pain. Don’t always believe everything you’re told!
-Dr. Brian Damhoff