Anatomical LLI refers to a leg which is physically shorter than the other due to unequal growth rates, fractures, or deformities. In a functional LLI situation, both legs may be identical in length (or nearly so), but one functions as if it were shorter because of either a postural imbalance in the body or uneven muscle contractions between the two legs. An example of a functional LLI could be something like this: say the structures in your right foot (arches, bones, muscles, tendons, etc.) are all working properly and holding up their side of your body in its correct and most stable position. However, your left foot has a collapsed arch, and the bones there have dropped to a less stable position, which causes your left foot to pronate (flare out) as you stand or walk. Your left leg now functions as if it were shorter because it isn't receiving the same amount of foot support as the right leg. This imbalance can cause pressure, stress, and pain in your knees, thighs, hips, pelvis, and spine (see "Functional" figure below).
Although many cases of LLI are very obvious and can be identified visually, a length difference of less than 25 mm (about an inch) usually cannot be detected on sight. In fact, you may have had a slight leg length inequality for years, and not even have known it.
Many medical researchers have concluded that even a few millimeters of LLI (a quarter of an inch or less) may be a primary or contributing cause of low back or hip problems, and an obvious stress factor in the legs.
If I don't know whether or not I have a leg length inequality, how can I find out?
Talk to your healthcare professional. He or she has procedures which can accurately measure the length of your legs and determine whether your condition is anatomical or functional. If you are found to have an LLI condition which is affecting your postural stability, your doctor can recommend a treatment program.
Depending on the diagnosis and treatment, your health care professional may recommend either a shoe lift or spinal/pelvic stabilizers (foot orthotics) to help you achieve postural balance and stability when you stand, walk, or run. Your healthcare professional will select the stabilizers best suited for you based on a variety of factors (lifestyle, health, age, weight, sex, etc.). And because many people wear at least two styles of shoes (dress and casual) each day, your healthcare professional may determine that an orthotics Combo (two pairs) would be best for your condition. If you do have an LLI condition, ask your doctor if stabilizers would help you.