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.
A patient?s legs may be different lengths for a number of reasons, including a broken leg bone may heal in a shorter position, particularly if the injury was severe. In children, broken bones may grow faster for a few years after they heal, resulting in one longer leg. If the break was near the growth center, slower growth may ensue. Children, especially infants, who have a bone infection during a growth spurt may have a greater discrepancy. Inflammation of joints, such as juvenile arthritis during growth, may cause unequal leg length. Compensation for spinal or pelvic scoliosis. Bone diseases such as Ollier disease, neurofibromatosis, or multiple hereditary exostoses. Congenital differences.
Many people walk around with LLD?s of up to 2 cm. and not even know it. However, discrepancies above 2 cm. becomes more noticeable, and a slight limp is present. But even up to 3 cm. a small lift compensates very well, and many patients are quite happy with this arrangement. Beyond 3 cm. however, the limp is quite pronounced, and medical care is often sought at that point. Walking with a short leg gait is not only unsightly, but increases energy expenditure during ambulation. It could also put more stress on the long leg, and causes functional scoliosis. Where the discrepancy is more severe, walking becomes grotesque or virtually impossible.
A doctor will generally take a detailed medical history of both the patient and family, including asking about recent injuries or illnesses. He or she will carefully examine the patient, observing how he or she moves and stands. If necessary, an orthopedic surgeon will order X-ray, bone age determinations and computed tomography (CT) scans or magnetic resonance imaging (MRI).
Non Surgical Treatment
You and your physician should discuss whether treatment is necessary. For minor LLDs in adults with no deformity, treatment may not be necessary. Because the risks may outweigh the benefits, surgical treatment to equalize leg lengths is usually not recommended if the difference is less than one inch. For these small differences, your physician may recommend a shoe lift. A lift fitted to the shoe can often improve your walking and running, as well as relieve back pain caused by LLD. Shoe lifts are inexpensive and can be removed if they are not effective. They do, however, add weight and stiffness to the shoe.
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 2-3 years before growth ends (around age 11-13), 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 required for several months. This surgery requires careful and continued follow-up with the surgeon to be sure that healing is going well.