Leg length discrepancy

Leg length discrepancy (LLD) means that one leg is longer than the other, a diagnosis that usually occurs in childhood.

The difference in lengths can vary widely. The larger the difference, and the younger the child, means a greater risk for problems in both the longer leg and shorter leg. Our pediatric orthopedists can help with leading-edge treatments like surgical lengthening procedures.

Dad crouching with young sonDad crouching with young son

Causes of leg length discrepancy

We might not know it, but most of us have a very slight difference in leg length of less than one centimeter, called normal leg length discrepancy. To determine variations in leg length, orthopedic specialists measure the distances between the anterior superior iliac spine and the medial malleolus in each leg. A proper diagnosis of LLD means there is a difference of up to several inches in difference between leg lengths, and rules out pelvic obliquity.

Among children, the known causes of LLD include:

  • A break or fracture to a leg bone that causes overgrowth of the bone as it heals.
  • A problem that is present at birth (congenital). For example, when the whole sides of the body are not equal.
  • Bone diseases like neurofibromatosis, multiple hereditary exostoses or Ollier disease.
  • Conditions that affect muscles and nerves, such as polio.
  • Infection.
  • Injury to the growth plate, a soft part of a long bone that allows the bone to grow.

If a larger LLD is not treated, problems can occur in the back, hips, knees and feet, including plantar fasciitis.

Treatment options for LLD

Your UCHealth orthopedic provider will work with you on a treatment plan that keeps in mind your child’s final height and leg lengths at skeletal maturity, not current leg lengths. We recommend treatment for LLDs predicted to be more than two centimeters at full height. For a final LLD predicted to be two centimeters or less at full height, we may only recommend regular check-ups by your orthopedic doctor.

Possible treatment options include:

Physical therapy. Exercises can strengthen and lengthen leg muscles, which may help correct LLD as your child grows.

Orthopedic shoe lift. Used to level the hips, and is often the only treatment needed for small discrepancies.

A child with a more significant LLD may need surgery that stops or slows growth in the longer leg, or lengthens the shorter leg.

Shortening may be done in one of two ways:

  • Epiphysiodesis. This procedures closes the growth plate of the long leg two to three years before growth ends, letting the short leg catch up.
  • Removing some bone from the longer leg once growth is complete.

Surgery to lengthen the shorter leg is more complicated than surgery to shorten a leg, but it usually has successful results. There are two types:

  • Internal limb-lengthening devices. We surgically implant a rod in the intramedullary canal of the tibia or femur. The rod has a magnetic metal spindle connected to a series of gears that can be activated by an external, remote-controlled device operated by the patient. This rod can either lengthen or shorten at one millimeter a day, repairing the LLD. The shortening function can also be used for soft tissue problems or to stimulate additional bone formation. We usually remove the device 12 to 24 months after implantation, when the bone has fully healed.
  • External fixation. Better for patients needing limb lengthening who have previous implants, associated deformities, an active infection or other factors. The fixator consists of two or more rings connected to six telescopic struts that can be lengthened or shortened according to your treatment plan.

A good prognosis

Treatment for leg length discrepancy is usually very successful, and your child can expect to have no activity restrictions.

Starting a personalized treatment now will ensure that LLD won’t keep your child from doing the activities he or she loves.

Girl about to kick soccer ball