Having one leg shorter than the other is a common physical condition. It has two primary causes--structural or functional problems. Structural differences in length can be the result of growth defect, previous injuries or surgeries. Functional differences in length can result from altered mechanics of the feet, knee, hip and/or pelvis. These altered mechanics from functional leg length discrepancy often stem from having an unbalanced foundation.
The causes of LLD are many, including a previous injury, bone infection, bone diseases (dysplasias), inflammation (arthritis) and neurologic conditions. Previously broken bones may cause LLD by healing in a shortened position, especially if the bone was broken in many pieces (comminuted) or if skin and muscle tissue around the bone were severely injured and exposed (open fracture). Broken bones in children sometimes grow faster for several years after healing, causing the injured bone to become longer. Also, a break in a child?s bone through a growth center (located near the ends of the bone) may cause slower growth, resulting in a shorter extremity. Bone infections that occur in children while they are growing may cause a significant LLD, especially during infancy. Bone diseases may cause LLD, as well; examples are neurofibromatosis, multiple hereditary exostoses and Ollier disease. Inflammation of joints during growth may cause unequal extremity length. One example is juvenile rheumatoid arthritis. Osteoarthritis, the joint degeneration that occurs in adults, very rarely causes a significant LLD.
The effects vary from patient to patient, depending on the cause of the discrepancy and the magnitude of the difference. Differences of 3 1/2 to 4 percent of the total length of the lower extremity (4 cm or 1 2/3 inches in an average adult), including the thigh, lower leg and foot, may cause noticeable abnormalities while walking and require more effort to walk. Differences between the lengths of the upper extremities cause few problems unless the difference is so great that it becomes difficult to hold objects or perform chores with both hands. You and your physician can decide what is right for you after discussing the causes, treatment options and risks and benefits of limb lengthening, including no treatment at all. Although an LLD may be detected on a screening examination for curvature of the spine (scoliosis), LLD does not cause scoliosis. There is controversy about the effect of LLD on the spine. Some studies indicate that people with an LLD have a greater incidence of low back pain and an increased susceptibility to injuries, but other studies refute this relationship.
The only way to decipher between anatomical and functional leg length inequalities (you can have both) is by a physical measurement and series of biomechanical tests. It is actually a simple process and gets to the true cause of some runner?s chronic foot, knee, hip and back pain. After the muscles are tested and the legs are measured it may be necessary to get a special X-ray that measures both of your thighs (Femurs) and legs (Tibias). The X-ray is read by a medical radiologist who provides a report of the actual difference down to the micrometer leaving zero room for error. Once the difference in leg length is known, the solution becomes clear.
Non Surgical Treatment
In an adult, we find that we can add a non compressive silicone heel lift to a shoe in increments of 3-4 mm maximum per week. Were we to give a patient with a 20 mm short leg, 20 mm of lift all at once, their entire body would rebel. The various compensations that the body has made, such as curvatures and shortening of muscles on the convex side of the curve, would make such a dramatic change not just noticeable, but painful. When we get close to balancing a patient by lifting a leg with heel inserts, then we perform another gait analysis and follow up xray. At that point, we can typically write them a final prescription to have their shoe modified. A heel lift is typically fine up to 7 mm. When it gets higher than that, the entire shoe must be modified. There are two reasons for this. The back of the shoe is generally too short to accommodate more than 7-8 mm inserted inside the shoes and a heel lift greater than 7 mm will lead to Achilles tendon shortening, which then creates it?s own panoply of problems.
Many people undergo surgery for various reasons - arthritis, knee replacement, hip replacement, even back surgery. However, the underlying cause of leg length inequality still remains. So after expensive and painful surgery, follow by time-consuming and painful rehab, the true culprit still remains. Resuming normal activities only continues to place undue stress on the already overloaded side. Sadly so, years down the road more surgeries are recommended for other joints that now endure the excessive forces.