What Is Anatomic Leg Length Inequality (ALLI)?
Anatomic leg length inequality (ALLI) is a condition where one leg is physically shorter than the other. When a person with this condition is in the standing position, it results in an unlevel pelvis and/or sacrum (the bone that sits under the spine), off-centering of the ribcage, and tilting of the shoulders and head. See Figure 1.
Who Does Anatomical Leg Length Inequality Affect?
Approximately one out of five, or 20% of, people have an anatomical short leg of at least 10 mm.1 However, when measuring at the level of the sacral base (the bone that forms the foundation for the spine) 40% of patients were found to have ALLI.2
Figure 2 shows an x-ray of a patient with both unleveling of the sacral base and tops of the legs. You will see that the tops of the legs are not as unlevel as the sacral base.
What Causes Anatomical Leg Length Inequality?
An anatomical short leg commonly results in a crooked spine in the low back region. See Figure 1. People with this anatomic leg length inequality often have low back pain, hip pain, pain radiating down the leg and/or knee pain.3 Pain may also be in the mid-back and neck from a short leg.
Common Causes of an anatomical short leg include:
- Often times a person with an anatomical short leg just developed that way. Simply, one leg did not grow to be as long at the other.
- Traumatic injuries can also cause anatomic leg length inequality, particularly during childhood and when the trauma is to the “growth plate” of one of the leg bones. This particular type of trauma will cause a slower rate of growth of the length of the bone as the child ages.
- Another increasingly common cause of ALLI is “iatrogenic”, or physician caused. Some patients undergo total hip arthroplasty, or a total hip replacement, and the resultant artifical joint was made to the wrong length, resulting in ALLI. Many of these people did not have ALLI previously. This occurs unintentionally as it is difficult to judge the size of the prosthetic to be placed in the femur of the replaced hip side. See Figure 3.
- Other conditions that can contribute a small amount to a short leg include:
- Thinning of the joint spaces of the hip or knee on one side only. This type of inequality would develop during adulthood, when these types of degenerative changes are a common problem.
- A “fallen arch” of one foot could also contribute to ALLI. These last two types would, however, result in minimal amount of inequality.
Figure 3. X-ray of the pelvis in a person showing unleveling of the tops of the legs (femurs) due to surgical intervention. This is called ‘iatrogenic induced short leg’ and occurs as an unintentional consequence.
Examination Procedures for the Diagnosis of Anatomic Leg Length Inequality
Some doctors will only evaluate and measure anatomic leg length inequality with visual inspection, that is, merely looking at the level of the patient’s pelvis as the patient stands in front of them. To measure the amount of discrepancy, small solid blocks are placed under the foot of the short leg until the pelvis “appears” level. This method of identification and measurement are not very accurate. Research has shown that this method is only accurate to a ½ inch. This is not very good since the vast majority of people with an anatomic short leg have a discrepancy less than a ½ in.
The only method that has been shown to consistently have valid and reliable results is the use of standing radiographs or x-rays of the pelvis and legs. See Figure 4. This method, along with tested line drawing analysis, has been shown to be accurate within a 1-2 mm.
Figure 4. The Femur Head Radiographic or x-ray view is typically taken at 40 inches with the tube and central ray at the height of the femur heads and parallel with the leveled floor. The x-ray cabinet/holder must be level and the floor must be level in order for accurate measurements to be made.
Common Chiropractic & Other Conservative Treatments
Because one leg is physically shorter than the other, chiropractic adjustments will not correct an anatomical leg length inequality. This is in contrast to chiropractors who use a “functional” short leg length analysis which is done with the patient lying on their stomach or back. However, Chiropractic adjustments can help the symptoms and or impairments of a patient with an anatomical short leg.
To reduce the body unleveling and pains due to an anatomic short leg, it must be measured accurately and an appropriate thickness heel lift or custom built orthotic should be placed under the foot of the short leg side. See Figure 5.
Figure 5. Different types of shoe lifts available are available to level the anatomical short leg. In A (left), a rigid rubber lifts is shown. In B (middle), a leather and slightly deformable rubber lift is shown. The lift in the middle is general considered the most comfortable by our patient populations. In C (right), a deformable felt lift is shown. However, the felt lifts are very affordable and readily placed in the majority of shoe types.
Common Medical Interventions
If an anatomic leg length inequality is particularly large (approaching 2 inches), a surgical procedure to remove a predetermined length of the femur (the thigh bone) on the side of the long leg is an option. This procedure is reserved only for the largest of the discrepancies.
Chiropractic Care May Have a Positive Influence on ALLI
Studies have shown that appropriate analysis and recommendation of a heel lift/orthotic device results in decreased pain and improved function for patients.3-13 When combined with the positive benefits of Chiropractic BioPhysics® (CBP®) care aimed at posture and spine correction, improvement of anatomical leg length related pain is likely. To see if you have a short leg or unlevel pelvis and to get relief of the-related symptoms, find a certified CBP® chiropractor near you.
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The primary purpose of this list of and general discussion of health conditions is to inform the public of the possibility that use of Chiropractic care may be associated with positive improvements in a variety of health conditions for patients actively undergoing Chiropractic care. Many of these symptoms require co-management and/or referrals to other health care specialists. This information is not intended, nor should it be used, to diagnose or treat any individual’s unique health condition.