The idea of having a leg length discrepancy and how it might relate to back pain or other issues is something that comes up in the clinic all the time. Having a difference in leg lengths is quite common though for the most part these will only be noticeable when lying on the couch rather than when standing as they aren’t congenital, that is to say there isn’t a difference in the length of the bones. The apparent difference comes from tension in the soft tissues of the thigh and hip which pull on the femur and/or pelvis giving the appearance of a difference in length between the two legs.
So the question is how does having a leg length discrepancy effect how you move and is it causing your back pain?
In this paper The effect of leg length discrepancy on pelvis and spine kinematics during gait it was found that there was minimal effect on how the pelvis and spine, lumbar through thoracic, moved even with up to a 3cm difference in leg length. Whilst the sample group was small, only 7 participants, the results were such that it pointed strongly towards leg length having no effect.
In another study the Relationship between mechanical factors and incidence of low back pain also found that a number of mechanical factors, including leg length discrepancy, pelvic tilt and lumbar lordosis, had little relationship to lower back pain. This time the study was quite a bit larger, 600 participants. What they did find though was that the endurance of the spinal extensors did have a strong relationship with lower back pain.
The take home from this is if someone has told you you have a leg length difference, don’t worry about it it is unlikely to be casing any great problems for you.
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