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?
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.