The majority of people in the world actually have some degree of leg length discrepancy, up to 2cm. One study found that only around 1/4 of people have legs of equal lengths. LLD of greater than 2cm is relatively rare, however, and the greater the discrepancy, the greater the chances of having a clinical problem down the road. A limp generally begins when LLD exceeds 2cm and becomes extremely noticeable above 3cm. When patients with LLD develop an abnormal gait, one of the debilitating clinical features can be fatigue because of the relatively high amount of energy needed to walk in the new, inefficient way. Poliomyelitis, or polio, as it is more commonly known, used to account for around 1/3 of all cases of LLD, but due to the effectiveness of polio vaccines, it now represents a negligible cause of the condition. Functional LLD, described above, usually involves treatment focused on the hip, pelvis, and/or lower back, rather than the leg. If you have been diagnosed with functional LLD or pelvic obliquity, please ask your orthopaedic surgeon for more information about treatment of these conditions.
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.
LLD do not have any pain or discomfort directly associated with the difference of one leg over the other leg. However, LLD will place stress on joints throughout the skeletal structure of the body and create discomfort as a byproduct of the LLD. Just as it is normal for your feet to vary slightly in size, a mild difference in leg length is normal, too. A more pronounced LLD, however, can create abnormalities when walking or running and adversely affect healthy balance and posture. Symptoms include a slight limp. Walking can even become stressful, requiring more effort and energy. Sometimes knee pain, hip pain and lower back pain develop. Foot mechanics are also affected causing a variety of complications in the foot, not the least, over pronating, metatarsalgia, bunions, hammer toes, instep pain, posterior tibial tendonitis, and many more.
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
After the leg length discrepancy has been identified it can be categorized in as structural or functional and appropriate remedial action can be instigated. This may involve heel lifters or orthotics being used to level up the difference. The treatment of LLD depends on the symptoms being experienced. Where the body is naturally compensating for the LLD (and the patient is in no discomfort), further rectifying action may cause adverse effects to the biomechanical mechanism of the body causing further injury. In cases of functional asymmetry regular orthotics can be used to correct the geometry of the foot and ground contact. In structural asymmetry cases heel lifts may be used to compensate for the anatomic discrepancy.
Surgery is another option. In some cases the longer extremity can be shortened, but a major shortening may weaken the muscles of the extremity. In growing children, lower extremities can also be equalized by a surgical procedure that stops the growth at one or two sites of the longer extremity, while leaving the remaining growth undisturbed. Your physician can tell you how much equalization can be attained by surgically halting one or more growth centers. The procedure is performed under X-ray control through very small incisions in the knee area. This procedure will not cause an immediate correction in length. Instead, the LLD will gradually decrease as the opposite extremity continues to grow and "catch up." Timing of the procedure is critical; the goal is to attain equal length of the extremities at skeletal maturity, usually in the mid- to late teens. Disadvantages of this option include the possibility of slight over-correction or under-correction of the LLD and the patient?s adult height will be less than if the shorter extremity had been lengthened. Correction of significant LLDs by this method may make a patient?s body look slightly disproportionate because of the shorter legs.