Unequal leg length (also termed leg length inequality, LLI or leg length discrepancy, LLD) is 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 ca ...

s are either different lengths or appear to be different lengths because of misalignment. It has been estimated that at least 0.1% of the population have a difference greater than .

Classification

There are two main types of leg length inequalities: * Structural differences are caused by the legs themselves being measurably different in length, usually due to differences in the length of the

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

in the thigh or the

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

and

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

bones in the lower leg. This may be a

birth defect A birth defect, also known as a congenital disorder, 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 ...

or it may occur after a

broken leg The human leg, in the general word sense, is the entire lower limb of the human body, including the foot, thigh or sometimes even the hip or gluteal region. However, the definition in human anatomy refers only to the section of the lower li ...

, serious infection, or local damage to one of the

growth plate The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a hyaline cartilage plate in the metaphysis at each end of a long bone. It is the part of a long bone where new bone growth takes place; that is, the whole bone is alive, wi ...

s in a leg. * The other, more common, type is seen when the legs themselves are the same length, but due to neuromuscular injuries in the

pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

or upper leg, one leg or hip is held higher and tighter than the other (

hypertonicity In chemical biology, tonicity is a measure of the effective osmotic pressure gradient; the water potential of two solutions separated by a partially-permeable cell membrane. Tonicity depends on the relative concentration of selective membrane- ...

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 leg. 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. Also, at least in United States, standard workup in children also includes

X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 Picometre, picometers to 10 Nanometre, nanometers, corresponding to frequency, ...

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 A leg length difference can result from a pelvic torsion. Abnormal (gravity drive) pronation will drive the innominate bones forward (anteriorly). The forward rotation of the innominate will shorten the leg (See Rothbart 2006). 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 is believed to cause low back pain as a result of increased pelvic obliquity and lumbar scoliosis.

Treatment

The most common treatment for discrepancies in leg length is the use of a simple heel lift, which can be placed within the shoe. In cases where the length discrepancy is moderate, an external build up to the shoe is usually more comfortable. 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 Distraction osteogenesis (DO), also called callus distraction, callotasis and osteodistraction, is a process used in orthopedic surgery, podiatric surgery, and oral and maxillofacial surgery to repair Skeleton, skeletal Deformity, deformities and ...

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 has esoteric origins and is based on several pseudosci ...

tool in their

Activator technique The Activator Method Chiropractic Technique is a chiropractic treatment method and device created by Arlan Fuhr as an alternative to manual spinal manipulation, manipulation of the spine or extremity joint manipulation, joints. The device is catego ...

, 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 atte ...

technique, since legs are usually of unequal length, 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. Another

confounding factor In statistics, a confounder (also confounding variable, confounding factor, extraneous determinant or lurking variable) is a variable that influences both the dependent variable and independent variable, causing a spurious association. Con ...

is that simply moving the two legs held together and leaning them imperceptibly to one side or the other produces different results.. Video discusses

and leg length Clinical measurement of leg length conventionally uses the distance from the

anterior superior iliac spine The anterior superior iliac spine (abbreviated: ASIS) is a bony projection of the iliac bone, and an important landmark of surface anatomy. It refers to the anterior extremity of the iliac crest of the pelvis. It provides attachment for the ingui ...

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 promine ...

. 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). It is supported by the femoral neck. Structure The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a l ...

to the center of the plafond of the distal

References

Rothbart BA 2006. Relationship of Functional Leg-Length Discrepancy to Abnormal Pronation. Journal American Podiatric Medical Association;96(6):499-507

External links