What is a short leg?
A short leg, or anatomical leg length inequality (LLI), is when the actual bony length of one lower limb differs from that of the other (that is a difference in the length of the femur or tibia from left to right). Research indicates that up to 3 mm of difference is ideal but that even 5 mm of difference increases the probability of low back pain significantly.
In an adult, a short leg cannot be corrected without surgery, but it often can be effectively compensated for with a correctly calculated shoe lift under one heel.
In a child, a short leg often can usually be grown out given correct treatment if aged 11 years or less for girls and 13 years or less for boys. Typically, correction will take place at 1 mm per month. We have however successfully corrected an 11 mm short leg in a 15 year old boy (over 12 months). We are experienced in this work and have had much success.
Please note that this is a bony length difference accurately measured using special x-rays. Do not confuse with an apparent leg length difference as observed when lying down due to muscle imbalance or inaccurately measured using a measuring tape. While this may be manipulated away and ‘fixed’ in a visit or two, a true short leg cannot.
Problems caused or aggravated by a short leg
Lower back pain is the greatest problem caused by leg length inequality. Ora Friberg, M.D. published an article titled “Clinical Symptoms and Biomechanics of Lumbar Spine and Hip Joint in Leg Length Inequality”, in Spine, 1983 (Vol. 8 Number 6 Pages 643-651) The study examined 798 chronic low back pain patients with a control group of 359 non-low back pain patients, and checked carefully for leg length differences.
Dr. Friberg found that 43.5% of the control group had leg length differences of 5mm or more, but that 75.4% of the chronic back pain patients had leg length inequality of 5mm or more. The conclusion is that leg length inequality can be a significant cause of chronic low back pain.
Leg length difference is also often a causative factor in pain in the hip, knee or leg on the side of the longer leg. Studies have shown that the longer leg carries more weight, and is subject to more abuse in activities such as walking, or running. Long term leg length inequality has also been shown to lead to hip joint arthritis.
Because of these complications, healthcare specialists believe that anyone suffering from chronic lower back pain, hip, knee, or leg pain should be evaluated for leg length difference as part the diagnostic process.
What causes a short leg?
A short leg can be caused by:
- Fracture – especially if involving the growth plate of the bone
- Infection – again, especially if involving the growth plate
- Polio (very rare)
- Wilms’ tumour of the kidney (very rare)
- Inheritance – genetic and other hereditable factors
- Poor postural habits – especially standing on one leg. The leg stood on grows less due to Heuter-Volkmann’s law. Unfortunately, once one has a short leg, it is more comfortable for the spine to stand on that leg, so further retarding the growth.
- Subluxation of lower lumbar spine and/or pelvis
The last two are in our experience the most common causes.
How to accurately measure a short leg
The leg length inequality must be measured both accurately and in a meaningful manner. The best way to measure a short leg in terms of its effect on the spine is using an x-ray with a Ferguson or semi-Ferguson view. Calculations are done to determine how much lift is required to level the base of the spine. A second confirming view is taken with the calculated lift in place to check the base of the spine is now level. The two x-rays should match with each other to within 2 mm to confirm all measurements are accurate.
If still growing (Children)
There is a good probability in many cases of correction. This will involve:
- Correction of any subluxation in the lumbar spine and pelvis
- Wearing of a lift on the short leg (to interrupt the postural habit of standing on that leg)
- Comparative x-rays to confirm progress and completion of correction.
- Ensure the child sits symmetrically (particularly avoiding sitting on one foot) Typically if correction will occur, it will take place at 1 mm per month.
If finished growing (Adults)
While correction is not possible, compensation using a lift is essential to avoid accelerated degeneration of the lumbar spine, hip or knee. Such a lift needs to be carefully calculated to suit the individual.
Corrective care is our specialty at Dr Richard Chiropractic so we have all the tools and facilities required to properly manage and reduce a short leg.