LEG LENGTH INEQUALITY research
A Study of Lower Extremity Length Inequality
Chiropractors are certainly not the only doctors interested in Leg Length Inequality Research. More than 60 years ago radiologists were researching the subject. (American Journal of Roentgenology and Radium TherapyVol. 51, No. 5, November 1946, 616-623) 1000 American soldiers complaining of LBP were sent for X-rays. After meticulous study and measurement, the reseachers concluded that: “it is possible to accurately measure differences in lower extremity lengths as manifested by a difference in the heights of the femoral heads.” The greatest difference in leg length measured was 44 mm.
How common is a short leg?
In young men suffering from LBP, the authors of this Leg Length Inequality Research paper found that: 23% of the soldiers had legs of equal length.The rest of the soldiers (77%) had unequal leg lengths, as follows: - 1 – 5 mm Short Leg: 39.5%
- 6 – 10 mm Short Leg: 22.5%
- 11 – 21 mm Short Leg: 13.3 %
- More than 22 mm Short Leg: 1.7%
The incidence of short right vs left legs was nearly equal. The average shortening was slightly more than 7 mm.
Pelvic tilt and Scoliosis
Concerning spinal biomechanical function, these authors noted that the short leg was associated with a tilt of the pelvis and a scoliosis. The authors noted: - The roentgenograms were made in the upright position with the use of a stabilization device.
Whenever there is a pelvic tilt, “there exists coincidentally a scoliosis of the lumbar spine.”
- “Because this scoliosis, in all instances, compensates for the tilt of the pelvis, it is referred to by us as compensatory scoliosis.”
- “The existence of this compensatory scoliosis in the presence of a tilted pelvis due to shortening of one or the other lower extremity is believed by us to have clinical significance and, furthermore, it is our opinion that the existence of any such condition cannot be determined with any degree of accuracy on gross physical examination.” [Important]
- “Furthermore, it becomes immediately apparent that the making of roentgenograms of the lumbosacral spine in the recumbent position, as is frequently done, completely prevents the discovery of such pathology as this.”
- “It was a general consistent observation that the degree of scoliosis was proportionate to the degree of pelvic tilt. An individual who has a shortened leg will have to compensate completely if he intends to hold the upper portion of his body erect or in the midsagittal plane.”
- “A consistent observation which has been made is that in those cases with a shortened leg there is a corresponding tilt of the pelvis and a compensatory scoliosis of the lumbar spine.”
Non-compensatory scoliosis
Of the 770 observed short leg cases seen in this study, only 8 had non-compensatory scoliosis. These scoliosis deformities were associated with pathology such as bony changes from old trauma to the disc, facet, or vertebral body, and these authors defined them as structural scoliosis.
When is a LLD clinically significant?
Leg length differences exceeding 5 mm were associated with greatest low back pain or disability, and therefore 5 mm is labeled as being a “marked difference.” The authors of this remarkable Leg Length Inequality Research paper stated further:
"It is our opinion that the existence of a short leg exceeding 5 mm is significant from the standpoint of symptomatology and disability.”
Associated findings of Leg Length Inequality Research
Sacroiliac Joint Arthritis 5.5% Increased Lumbosacral Angle Above 50° 4.3% Lumbosacral Transitional Segment 3.7% Pars Defect With Spondylolisthesis 2.7% Reduced Lumbar Lordosis 2.5% L5-S1 Facet Tropism 1.5% Pars Defect But No Spondylolisthesis 1.0% L5-S1 Retrolisthesis 0.6%
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LLI and Low Back Pain / Neck Pain
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