Anatomical leg length inequality (anisomelia) is the difference in actual bone and joint length between legs. In some studies, as little as 5mm (3/16") difference is considered significant, and can affect the successful outcome of chronic low back pain treatment.

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.

Authorities suggest the treatment of chronic low back pain complicated by anisomelia might be a two-part process:

- First, spinal and tissue manipulation to reduce misalignments and muscular tightness in the lower back and pelvis, which are normal occurrences with leg length inequality.

- Second, utilization of a heel lift under the short leg side to stabilize and level the pelvis, thereby giving the spine a more level foundation on which to rest. A level foundation reduces wedging of the intervertebral discs, sheer stress on the spinal joints, rotational distortions of the vertebrae, and normalizes lower back muscular balance.

This two-step process helps reduce the most chronic low back and hip pain problems in a high percentage of cases.

There is some controversy in the healthcare industries as to the effects of leg length discrepancy; some studies do not show a strong statistical link between lower back pain and leg length difference. While it is true that some people can accommodate to up to 3/4" of leg length difference without short-term ill effects, over time, many people find that even 5mm of leg length difference can cause severe sacroiliac, hip, and lower spine problems.

Leg length discrepancy recently acquired as a result of accidental or surgical causes is probably best compensated by the full amount of the difference, using heel or full-foot shoe lifts. Hip and knee replacement patients often require some degree of leg length compensation after stabilization.

More chronic leg length differences often need reduction of only half the measured leg length difference using lifts, as the body will have accommodated to a great degree, and any sudden change in that balance can cause secondary problems. Heel inserts used to compensate for long-term leg length differences should be introduced gradually; adding only 2-3mm to the shorter leg each week, to allow the body to achieve a new balance.

Even though it is an important factor, leg length inequality is commonly overlooked in the evaluation of low back, hip, and leg pain problems. Anyone with back, hip, or leg pain should have a thorough examination to determine if leg length inequality is a factor in their condition.