Unequal leg length (also termed leg length inequality, LLI or leg length discrepancy, LLD) is often a disabling condition where the

leg A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element cap ...

s are either different lengths (structurally), or appear to be different lengths, because of misalignment (functionally). Unequal leg length with a very small degree of difference can be common; small inequalities in leg length may affect 40%-50% of the human population. It has been estimated that at least 0.1% of the population have a difference greater than . , that is approximately 8.1 million people total in the human population.

Classification

There are two main types of leg length discrepancy: * ''Structural'' differences are caused by the leg bones themselves being measurably different in length. Usually due to differences in the length of the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

in the thigh or the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

and fibula bones in the lower leg. This may be a

birth defect A birth defect is an abnormal condition that is present at birth, regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can range from mild to severe. Birth de ...

or it may occur after a broken leg, serious infection, or local damage to one of the growth plates in that particular leg causing a disruption to normal growth due to traumatic injury, and/or ineffectual recovery from such injury. * The other, more common, type called a ''functional'' leg difference, and is seen when the legs themselves are the same length, but due to neuromuscular injuries in the

pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

or upper leg, one leg or hip is held higher and tighter than the other ( hypertonicity in the musculature of the pelvis or leg). These unequally tightened muscles cause the legs to seem to be different lengths, even though careful measurement would show equal lengths of the actual bones within the leg or legs. This is called leg length alignment asymmetry (LLAA) and can be seen while lying down.

Diagnosis and workup

Unequal leg length in children is frequently first suspected by parents noticing a limp that appears to be getting worse. The standard workup in children is a thorough physical examination, including observing the child while walking and running. In the United States, standard workup in children also includes

X-rays An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

to quantify actual length of the bones of the legs. On X-rays, there is generally measurement of both the

and the

, as well as both combined. Various measuring points for these have been suggested, but a functional method is to measure the distances between joint surfaces: *Femur length: The superior aspect of the femoral head and the distal portion of the medial femoral condyle. *Tibial length: The medial tibial plateau and the tibial plafond As previously mentioned, leg length difference can result from a repetitive activity that misaligns, one example being pelvic torsion; this is a functional LLD. Abnormal (gravity drive)

pronation Motion, the process of movement, is described using specific anatomical terminology, anatomical terms. Motion includes movement of Organ (anatomy), organs, joints, Limb (anatomy), limbs, and specific sections of the body. The terminology used de ...

will drive the innominate bones forward (anteriorly). The forward rotation of the innominate will shorten the leg. The more pronated foot will have the more forwardly rotated innominate bone and will be the side with the functionally short leg. In adults, leg length discrepancy causes pain and challenge to the kinetic chain of the body's structure and almost every other part of the body – even organs because of the spaces and connection the nerves demand throughout the joints of the body. They may therefore become impaired and can become dysfunctional, according to the severity of differentiation in the discrepancy. Balance issues often cause muscle deconditioning as the spinal column tries to compensate and bend more than is safe for the joint and nerve spacing in the spinal column, leading to more denervation and weakness. The increased weight and pressure of the longer leg on the shorter leg often leads to denervation and weakness.

Sciatica Sciatica is pain going down the leg from the lower back. This pain may go down the back, outside, or front of the leg. Onset is often sudden following activities such as heavy lifting, though gradual onset may also occur. The pain is often desc ...

and blood circulation in the lower limbs is impaired as well.

Low back pain Low back pain or wiktionary:lumbago#Etymology, lumbago is a common musculoskeletal disorders, disorder involving the muscles, nerves, and bones of the back, in between the lower edge of the ribs and the lower fold of the buttocks. Pain can var ...

will occur with increased pelvic obliquity; X-rays of the sacroilliac joint may help determine joint impingement and any lumbar

scoliosis Scoliosis (: scolioses) is a condition in which a person's Vertebral column, spine has an irregular curve in the coronal plane. The curve is usually S- or C-shaped over three dimensions. In some, the degree of curve is stable, while in others ...

that often, if not always, occurs.

Treatment

The most common treatment for discrepancies in leg length is the use of a simple heel lift; this is outdated, and may lead to foot cramping and discomfort. The modern remedy is a full orthotic insole or outsole lift which can be placed inside or outside the shoe. In cases where the length discrepancy is moderate, an external build up to the shoe is necessary to accommodate the foot spacing in most modern shoes. An improved method for addressing differences in leg length involves measuring and rectifying the disparities while standing upright and weight bearing. Adjustments of minor or significant biomechanical change can be made to the foot's angle and height to correct the discrepancies in real-time using a mechanical device like the Vertical Foot Alignment System (VFAS). This technique will take into account the changes that the foot goes through when under a weight-bearing condition including correct foot alignment, arch support and comfort. Custom shoes

In severe cases, surgery can be used to make the longer leg shorter (or impede its growth), and/or make the shorter leg longer via limb lengthening.

Measurement challenges

Although prone "functional leg length" is a widely used

chiropractic Chiropractic () is a form of alternative medicine concerned with the diagnosis, treatment and prevention of mechanical disorders of the musculoskeletal system, especially of the spine. It is based on several pseudoscientific ideas. Many c ...

tool in their Activator technique, it is not a recognized

anthropometric Anthropometry (, ) refers to the measurement of the human individual. An early tool of physical anthropology, it has been used for identification, for the purposes of understanding human physical variation, in paleoanthropology and in various a ...

technique, since most legs are usually only to a small degree unequal, and measurements in the prone position are not entirely valid estimates of standing X-ray differences.D W Rhodes, E R Mansfield, P A Bishop, J F Smith
The validity of the prone leg check as an estimate of standing leg length inequality measured by X-ray.
''J Manipulative Physiol Ther.''; 18 (6):343-6 Measurements in the standing position are far more reliable. Since another

confounding factor In causal inference, a confounder is a variable that influences both the dependent variable and independent variable, causing a spurious association. Confounding is a causal concept, and as such, cannot be described in terms of correlati ...

is that simply moving the two legs held together and leaning them imperceptibly to one side or the other produces different results.. Video discusses Activator technique and leg length Clinical measurement of leg length conventionally uses the distance from the anterior superior iliac spine to the

medial malleolus A malleolus is the bony prominence on each side of the human ankle. Each leg is supported by two bones, the tibia on the inner side (medial) of the leg and the fibula on the outer side (lateral) of the leg. The medial malleolus is the promin ...

. Projectional radiographic measurements of leg length have two main variants:Page 269
in: *Teleroentgenogram, which projects the entirety of both legs at the same time. *Orthoroentgenogram, which takes separate images of the hip, knee and ankle. On X-rays, the length of the lower limb can be measured from the proximal end of

femoral head The femoral head (femur head or head of the femur) is the highest part of the thigh bone (femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the ...

to the center of the plafond of the distal

References

External links