Your child has been diagnosed with a leg-length discrepancy. This means that your child’s legs are slightly different lengths, with one leg longer than the other. The difference in lengths can vary widely. The larger the difference in lengths, and the younger the child, the more problems that can result as the child gets older. Because of this, your child may be referred to a pediatric orthopedist (doctor specializing in treating bone and joint problems in children) for evaluation and possible treatment.
LLDs are very common. Sometimes the cause isn’t known. But the known causes of LLD in children include:
Injury or infection that slows growth of one leg bone.
Injury to the growth plate (a soft part of a long bone that allows the bone to grow). Growth plate injury can slow bone growth in that leg.
Fracture to a leg bone that causes overgrowth of the bone as it heals.
A congenital (present at birth) problem (one whole side of the child’s body may be larger than the other side).
Conditions that affect muscles and nerves, such as polio.
The doctor carefully examines the child. He or she checks to be sure the legs are actually different lengths. This is because problems with the hip (such as a loose joint) or back (scoliosis) can make the child appear to have one shorter leg, even though the legs are the same length.
An X-ray of the child’s legs is taken. During the X-ray, a long ruler is put in the image so an accurate measurement of each leg bone can be taken.
If an underlying cause of the discrepancy is suspected, tests are done to rule it out.
Treatment for an LLD depends on the amount of difference and the cause, if known. The doctor will discuss treatment options carefully with you and your child before any decisions are made. It is important to note that treatment is planned with the child’s final height and leg lengths in mind, not the current leg lengths.
Treatment is generally not needed if the child’s final LLD is predicted to be 2 centimeters or less at full height. However, the child should return to an orthopaedic doctor periodically for reevaluation.
Treatment is often recommended for LLDs predicted to be more than 2 centimeters at full height. If treatment is done, it usually doesn’t begin until the child starts walking. Possible treatment options include:
A “lift” in one shoe to level the child’s hips. This is often the only treatment needed for small discrepancies.
Surgery to shorten the longer leg. This is less involved than lengthening the shorter leg. Shortening may be done in one of two ways:
Closing the growth plate of the long leg 2 to 3 years before growth ends (around age 11 to 13), letting the short leg catch up. This procedure is called an epiphysiodesis.
Taking some bone from the longer leg once growth is complete to even out leg lengths.
Surgery to lengthen the shorter leg. This surgery is more involved than surgery to shorten a leg. During this surgery, cuts are made in the leg bone. An external metal frame and bar are attached to the leg bone. This frame and bar slowly pull on the leg bone, lengthening it. The frame and bar must be worn constantly for months to years. When the frame and bar are removed, a leg cast is usually required for several months. This surgery requires careful and continued follow-up with the surgeon to be sure that healing is going well.
Physical therapy to strengthen and lengthen muscles. This is especially helpful after surgery.
A child with an LLD has no activity restrictions. Treatment of LLDs usually leads to a good outcome. If a larger LLD is not treated, back, hip, and knee problems often result as the child grows.