KidsMD Health Topics

Leg Length Discrepancy

  • Overview

    If one of your child's legs is longer than the other leg, he or she has a common problem known as leg length discrepancy. A typical difference in leg length can be anywhere from one centimeter, which usually does not cause any problems, to more than six centimeters. The greater the discrepancy, the more your child must compensate his or her normal posture and walking pattern in day to day life, which can lead to a variety of symptoms, such as functional scoliosis, hip, knee and ankle problems.

    There are generally two kinds of leg length discrepancies:

    • Structural discrepancy occurs when either the thigh (femur) or shin (tibia) bone in one leg is actually shorter than the corresponding bone in the other leg.
    • Functional discrepancy occurs when the leg lengths are equal, but symmetry is altered somewhere above the leg, which in turn disrupts the symmetry of the legs. For example, developmental dislocation of the hip (DDH) can cause a functional discrepancy. In DDH, the top of the leg bone (femur) that is not properly positioned in the hip socket may hang lower than the femur on the other side, giving the appearance and symptoms of a leg length discrepancy.

    How Boston Children's Hospital approaches leg length discrepancy

    Depending on the severity of your child's condition, doctors may or may not require surgery to treat the leg length discrepancy. But if the condition is severe enough to require surgery, doctors at Children's are committed to working with you and your child to weigh all the available options, taking into consideration recovery time, possible side effects and your child's individual physical needs.

    Boston Children's Hospital
    300 Longwood Avenue
    Fegan 2
    Boston MA 02115

  • In-Depth

    What causes a leg length discrepancy?

    • An injury, such as in a fracture that damages the cells responsible for growth of the bone, while the corresponding bone on the other leg grows normally. Some fractures can also lead to overgrowth of bone during the healing process. Overgrowth commonly occurs in young children with thighbone fractures.
    • Diseases of the bone, such as osteomyelitis, can injure a region in a bone, called the growth plate, where growth in length occurs, so that a discrepancy occurs gradually over time.
    • Some children are born with legs that are of unequal length or bowed tibias.
    • Bone tumors and treatments designed to eradicate them.
    • Functional leg length discrepancy can also result from congenital (present at birth) problems that alter alignment of the hips, such as coxa vara and developmental dislocation of the hip.
    • Neuromuscular problems, such as cerebral palsy, which causes problems with alignment and posture can also lead to a functional discrepancy.

    What are the symptoms of a leg length discrepancy?

    • One leg is obviously shorter than the other (although this is not always obvious).
    • Problems with posture (i.e. shoulder may tilt toward shorter side) leading to compensatory or functional scoliosis.
    • Gait problems, such as limping, toe-walking, or rotation of the leg. a knee that's chronically hyperextended on the short side and flexed on the long side.
    • Pain in the back hip, knee, and/or ankle.

    The symptoms of a leg length discrepancy vary widely and are often related to the underlying problem causing the discrepancy and the alignment problems that result from it. Keep in mind that every child experiences symptoms of this condition differently. Always consult a physician for a diagnosis.

  • Tests

    How does a doctor know my child has a leg length discrepancy?

    Diagnostic procedures include a complete medical history of the patient and a physical examination by an orthopedic surgeon. The doctor will use both of these tools to determine the underlying cause of the problem.

    During the physical exam, your child's doctor will probably take two measurements of your child's legs with a tape measure.

    • One measurement, to determine the "real" length of the leg will be taken from the middle of the hip down to the ankle.
    • The other, the "apparent" length, will be taken from the naval area. The discrepancy determined by these two measurements might be different if the "apparent" length is affected by hip position, suggesting a functional discrepancy.

    The doctor may also ask your child to stand with a block under the shorter leg to confirm the measurement estimate the amount of correction that feels best. The doctor will also want to confirm the measurement with the following diagnostic tests:

    • X-rays - A diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film
    • Computerized Tomography Scan (also called a CT or CAT scan) - A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce cross-sectional images (often called "slices"), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat and organs. CT scans are more detailed than general X-rays
  • Specific treatment for leg length discrepancy will be determined by your child's orthopedic surgeon based on

    • your child's age, overall health, and medical history
    • the extent of the discrepancy
    • your child's tolerance for specific medications, procedures, or therapies
    • expectations for the course of the condition
    • your opinion or preference.

    You and your child's feelings about the treatment are extremely important. Some techniques used to equalize leg length are simple and safe, but others, especially lengthening procedures, are complex with high complication rates. These require strict cooperation by you and your child for success.

    Much planning is involved in the early stages of managing a child with a leg length discrepancy.

    • Since children are still growing, the goal of treatment is to correct the discrepancy that would be present at maturity and not the present discrepancy.
    • Not all children grow at the same rate, so careful analysis of your child's personal rate of growth is crucial.
    • To estimate the discrepancy at maturity, your child's orthopedic surgeon may need to continually take measurements of your child's growth over a period of one or two years before any surgery can be considered.

    The goal of treatment is not always to have legs of equal length. For example, some patients, with neuromuscular conditions that involve muscle weakness or paralysis of the short leg, may do best with an under-correction of one or two cm. This slight discrepancy allows for clearing of the floor during the swing phase of the walking cycle.

    Generally speaking, discrepancies greater than two cm at skeletal maturity usually require some kind of intervention, because these will cause limping.

    Non-surgical treatment

    • Orthotics - shoe lift can be used to treat discrepancies from two to six cm.
    • Prosthetics – these devices, which are typically used to treat a child who has had to have an amputation, may be satisfactory for some patients with very large discrepancies, who would not benefit from other lengthening or shortening procedures.

    Surgical treatment

    Shortening procedures - The following procedures, used to shorten the longer leg, may be recommended for some children, in cases where the leg length discrepancy is expected to be between two and six cm at maturity. Shortening is considered safer and results in fewer complications than lengthening procedures:

    • Epiphysiodesis - This procedure slows the rate of growth of the long leg, allowing the short leg to catch up. The operation involves the creation of bony ridge, usually by repositioning a block of bone in the region that tethers the growth plate, preventing future growth. The disadvantages of this procedure include shortened stature, surgery on the unaffected extremity, and the irreversibility of the procedure.
    • Epiphyseal stapling - This operation is performed to slow the rate of the growth temporarily. Staples are surgically inserted on each side of the growth plate. Once equalization has been achieved, the staples are removed.
    • Bone resection - This operation, removal of a section of bone to equal out the discrepancy, can be performed in adults or adolescents who are no longer growing.

    Lengthening procedures - are usually reserved for discrepancies that are more than four cm. While one of the obvious advantages of lengthening is the achievement of a desirable height, it is not always the method of choice because the process used is technically difficult and has a significant rate of complications, discussed further below.

    A customized apparatus that encircles the leg is surgically attached to the limb that will be lengthened by pins. Limb lengthening correction works on the principle of bone regeneration (osteogenesis) as segments of the bone are pulled apart (distracted).

    • To achieve this, a bone is first cut in two during surgery.
    • Days after surgery, the two ends of the bone are very gradually pulled apart through continual adjustments that are made to the apparatus, usually at a rate of one mm per day. This gradual distraction leads to formation of new bone between the two ends, at the site of lengthening.
    • After the process in complete, and the bone is given a chance to harden, the apparatus is surgically removed.
    • A cast or brace may be required for some time for further protection.

    Common complications associated with lengthening procedures include

    • pin tract infection
    • wound infection
    • hypertension
    • partial dislocation of the hip and knee
    • a delayed union of the bone and fatigue fractures after removal of the lengthening apparatus.

    Physical therapy, designed to stretch muscles and maintain joint flexibility, is an important component to any surgeries used to correct leg length discrepancies. With proper treatment, your child will be able to resume all their normal activities.

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